[multiboot] Work around raw-flag bug in Solaris kernels

Solaris kernels are multiboot images with the "raw" flag set,
indicating that the loader should use the raw address fields within
the multiboot header rather than looking for an ELF header.  However,
the Solaris kernel contains garbage data in the raw address fields,
and requires us to use the ELF header instead.

Work around this by always using the ELF header if present.  This
renders the "raw" flag somewhat redundant.

src/arch/i386/image/multiboot.c

@@ -360,6 +360,13 @@ static int multiboot_load_raw ( struct image *image,
 	userptr_t buffer;
 	int rc;
 
+	/* Sanity check */
+	if ( ! ( hdr->mb.flags & MB_FLAG_RAW ) ) {
+		DBGC ( image, "MULTIBOOT %p is not flagged as a raw image\n",
+		       image );
+		return -EINVAL;
+	}
+
 	/* Verify and prepare segment */
 	offset = ( hdr->offset - hdr->mb.header_addr + hdr->mb.load_addr );
 	filesz = ( hdr->mb.load_end_addr ?
@@ -432,14 +439,14 @@ static int multiboot_load ( struct image *image ) {
 		return -ENOTSUP;
 	}
 
-	/* Load the actual image */
-	if ( hdr.mb.flags & MB_FLAG_RAW ) {
-		if ( ( rc = multiboot_load_raw ( image, &hdr ) ) != 0 )
-			return rc;
-	} else {
-		if ( ( rc = multiboot_load_elf ( image ) ) != 0 )
-			return rc;
-	}
+	/* There is technically a bit MB_FLAG_RAW to indicate whether
+	 * this is an ELF or a raw image.  In practice, grub will use
+	 * the ELF header if present, and Solaris relies on this
+	 * behaviour.
+	 */
+	if ( ( ( rc = multiboot_load_elf ( image ) ) != 0 ) &&
+	     ( ( rc = multiboot_load_raw ( image, &hdr ) ) != 0 ) )
+		return rc;
 
 	return 0;
 }