[prefix] Report both %esi and %ecx when opening payload fails

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

src/arch/i386/prefix/libprefix.S

@@ -746,6 +746,9 @@ a20_death_message:
 	xorw	%di, %di
 	movl	%esi, %eax
 	call	print_hex_dword
+	call	print_space
+	movl	%ecx, %eax
+	call	print_hex_dword
 	movw	$payload_death_message, %si
 	call	print_message
 2:	/* Halt system */

src/arch/i386/prefix/mromprefix.S

@@ -99,6 +99,7 @@ find_mem_bar:
 	jle	1f
 	stc
 	movl	$0xbabababa, %esi	/* Report "No suitable BAR" */
+	movl	rom_bar_size, %ecx
 	jmp	99f
 1:	movw	$4, %bp
 
@@ -157,7 +158,8 @@ find_mem_bar:
 	call	pci_write_config_dword
 
 	/* Locate our ROM image */
-1:	addr32 es cmpw $0xaa55, (%eax)
+1:	movl	$0xaa55, %ecx		/* 55aa signature */
+	addr32 es cmpw %cx, (%eax)
 	je	2f
 	stc
 	movl	%eax, %esi		/* Report failure address */