Introduce a header file for the BIOS emulator

We should have a public header so that users can avoid defining functions
themselves.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/ati_radeon_fb.c b/drivers/video/ati_radeon_fb.c
index 618f5d9..5748951 100644
--- a/drivers/video/ati_radeon_fb.c
+++ b/drivers/video/ati_radeon_fb.c
@@ -19,6 +19,7 @@
 #include <common.h>
 
 #include <command.h>
+#include <bios_emul.h>
 #include <pci.h>
 #include <asm/processor.h>
 #include <asm/errno.h>
@@ -544,7 +545,6 @@
 }
 
 #include "../bios_emulator/include/biosemu.h"
-extern int BootVideoCardBIOS(pci_dev_t pcidev, BE_VGAInfo ** pVGAInfo, int cleanUp);
 
 int radeon_probe(struct radeonfb_info *rinfo)
 {