[librm] Add meaningful labels at section changes

The mode-transition code involves paths which switch back and forth
between the .text and .text16 sections.  At present, only the start of
each function is labelled, which makes it difficult to decode
addresses within the parts of the function existing in a different
section.

Add explicit labels at the start of each section change, so that
addresses can be meaningfully decoded to the nearest label.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/transitions/librm.S

 	movl	%cr0, %eax
 	orb	$CR0_PE, %al
 	movl	%eax, %cr0
-	data32 ljmp	$VIRTUAL_CS, $1f
+	data32 ljmp	$VIRTUAL_CS, $r2p_pmode
 	.section ".text", "ax", @progbits
 	.code32
-1:
+r2p_pmode:
 	/* Set up protected-mode data segments and stack pointer */
 	movw	$VIRTUAL_DS, %ax
 	movw	%ax, %ds
 	movw	%ax, %fs
 	movw	%ax, %gs
 	movw	%ax, %ss
-	ljmp	$REAL_CS, $1f
+	ljmp	$REAL_CS, $p2r_rmode
 	.section ".text16", "ax", @progbits
 	.code16
-1:
+p2r_rmode:
 	/* Switch to real mode */
 	movl	%cr0, %eax
 	andb	$0!CR0_PE, %al
 
 	/* Switch to protected mode and move register dump to PM stack */
 	movl	$PC_OFFSET_END, %ecx
-	pushl	$1f
+	pushl	$pc_pmode
 	jmp	real_to_prot
 	.section ".text", "ax", @progbits
 	.code32
-1:
+pc_pmode:
 	/* Call function */
 	leal	PC_OFFSET_IX86(%esp), %eax
 	pushl	%eax
 
 	/* Switch to real mode and move register dump back to RM stack */
 	movl	$PC_OFFSET_END, %ecx
-	pushl	$1f
+	pushl	$pc_rmode
 	jmp	prot_to_real
 	.section ".text16", "ax", @progbits
 	.code16
-1:	
+pc_rmode:
 	/* Reload GDT and IDT, restore registers and flags and return */
 	movw	%sp, %bp
 	data32 lgdt (%bp)
 
 	/* Switch to real mode and move register dump to RM stack  */
 	movl	$( RC_OFFSET_RETADDR + 4 /* function pointer copy */ ), %ecx
-	pushl	$1f
+	pushl	$rc_rmode
 	jmp	prot_to_real
 	.section ".text16", "ax", @progbits
 	.code16
-1:
+rc_rmode:
 	/* Call real-mode function */
 	popl	rc_function
 	popal
 
 	/* Switch to protected mode and move register dump back to PM stack */
 	movl	$RC_OFFSET_RETADDR, %ecx
-	pushl	$1f
+	pushl	$rc_pmode
 	jmp	real_to_prot
 	.section ".text", "ax", @progbits
 	.code32
-1:
+rc_pmode:
 	/* Restore registers and return */
 	popal
 	ret