Add a PCI header to the VGA ROM if needed

Allows the ROM to be extracted from a PCI device.

V2: * Declare the PCI header in C
    * Replace #ifdef CONFIG_VGA_PCI with #if CONFIG_VGA_PCI == 1

Signed-off-by: Julian Pidancet <julian.pidancet@gmail.com>
diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S
index fbfa9f7..2dc07c1 100644
--- a/vgasrc/vgaentry.S
+++ b/vgasrc/vgaentry.S
@@ -12,6 +12,7 @@
         .code16gcc
 #include "vgaccode.16.s"
 
+#include "config.h" // CONFIG_*
 #include "entryfuncs.S" // ENTRY_*
 
 
@@ -30,7 +31,15 @@
 _rom_header_checksum:
         .byte 0
 _rom_header_other:
-        .space 21
+        .space 17
+_rom_header_pcidata:
+#if CONFIG_VGA_PCI == 1
+        .word rom_pci_data
+#else
+        .word 0
+#endif
+_rom_header_pnpdata:
+        .word 0
 
 
 /****************************************************************