[romprefix] Add more diagnostic messages to ROM prefix

Include PMM allocation result in POST banner.

Include full product string in "starting execution" message.

Also mark ourselves as supporting DDIM in PnP header, for
completeness.

src/arch/i386/prefix/romprefix.S

 #define PCI_SIGNATURE ( 'P' + ( 'C' << 8 ) + ( 'I' << 16 ) + ( ' ' << 24 ) )
 #define STACK_MAGIC ( 'L' + ( 'R' << 8 ) + ( 'E' << 16 ) + ( 'T' << 24 ) )
 #define PNP_GET_BBS_VERSION 0x60
+#define PMM_ALLOCATE 0x0000
 
 	.text
 	.code16
 	.byte	0x02			/* Device base type code */
 	.byte	0x00			/* Device sub-type code */
 	.byte	0x00			/* Device interface type code */
-	.byte	0x54			/* Device indicator */
+	.byte	0xf4			/* Device indicator */
 	.word	0x0000			/* Boot connection vector */
 	.word	0x0000			/* Disconnect vector */
 	.word	bev_entry		/* Boot execution vector */
 
 	/* Check for PnP BIOS */
 	testw	$0x0f, %bx	/* PnP signature must be aligned - bochs    */
-	jnz	hook_int19	/* uses unalignment to indicate 'fake' PnP. */
+	jnz	no_bbs		/* uses unalignment to indicate 'fake' PnP. */
 	cmpl	$PNP_SIGNATURE, %es:0(%bx)
-	jne	hook_int19
+	jne	no_bbs
 	/* Is PnP: print PnP message */
 	movw	$init_message_pnp, %si
 	xorw	%di, %di
 	call	print_message
-
 	/* Check for BBS */
 	pushw	%es:0x1b(%bx)	/* Real-mode data segment */
 	pushw	%ds		/* &(bbs_version) */
 	lcall	*%es:0xd(%bx)
 	addw	$8, %sp
 	testw	%ax, %ax
-	jne	hook_int19
-	movw	$init_message_bbs, %si
-	xorw	%di, %di
-	call	print_message
-	jmp	hook_bbs
-	/* Not BBS-compliant - must hook INT 19 */
-hook_int19:
+	je	got_bbs
+no_bbs:	/* Not BBS-compliant - must hook INT 19 */
 	movw	$init_message_int19, %si
 	xorw	%di, %di
 	call	print_message
 	pushw	%gs /* %gs contains runtime %cs */
 	pushw	$int19_entry
 	popl	%es:( 0x19 * 4 )
-hook_bbs:
+	jmp	bbs_done
+got_bbs: /* BBS compliant - no need to hook INT 19 */
+	movw	$init_message_bbs, %si
+	xorw	%di, %di
+	call	print_message
+bbs_done:
 
 	/* Check for PMM */
 	movw	$( 0xe000 - 1 ), %bx
 	pushw	$0x0006		/* Aligned, extended memory */
 	pushl	$0xffffffff	/* No handle */
 	pushl	$( 0x00200000 / 16 ) /* 2MB in paragraphs */
-	pushw	$0x0000		/* pmmAllocate */
+	pushw	$PMM_ALLOCATE
 	lcall	*%es:7
 	addw	$12, %sp
-	testw	%dx, %dx	/* %ax==0 even on success, since align=2MB */
-	jnz	gotpmm
-	movb	$'-', %al
+	movw	%dx, %ax
 	xorw	%di, %di
-	call	print_character
-	jmp	no_pmm
-gotpmm:	/* PMM allocation succeeded: copy ROM to PMM block */
+	call	print_hex_word
+	movw	%dx, ( image_source + 2 )
+	testw	%dx, %dx	/* %ax==0 even on success, since align=2MB */
+	jz	no_pmm
+	/* PMM allocation succeeded: copy ROM to PMM block */
 	pushal			/* PMM presence implies 1kB stack */
-	movw	%ax, %es	/* %ax=0 already - see above */
-	pushw	%dx
-	pushw	%ax
-	popl	%edi
-	movl	%edi, image_source
+	xorw	%ax, %ax
+	movw	%ax, %es
+	movl	image_source, %edi
 	xorl	%esi, %esi
 	movzbl	romheader_size, %ecx
 	shll	$9, %ecx
 	.size init, . - init
 
 init_message:
-	.asciz	"gPXE (http://etherboot.org) - PCI "
+	.asciz	"gPXE (http://etherboot.org) - "
 	.size	init_message, . - init_message
 init_message_pci:
 	.asciz	" PCI"
  */
 bbs_version:
 	.word	0
+	.size	bbs_version, . - bbs_version
 
 /* Boot Execution Vector entry point
  *
 	popw	%ds
 
 	/* Print message as soon as possible */
-	movw	$exec_message, %si
+	movw	$prodstr, %si
 	xorw	%di, %di
 	call	print_message
+	movw	$exec_message, %si
+	call	print_message
 
 	/* Store magic word on BIOS stack and remember BIOS %ss:sp */
 	pushl	$STACK_MAGIC
 	.previous
 
 exec_message:
-	.asciz	"Entering gPXE\n"
+	.asciz	" starting execution\n"
 	.size exec_message, . - exec_message
 
 /* UNDI loader