soc/intel/baytrail: Drop invalid `VGA_BIOS_FILE` default

This file does not exist in the coreboot tree. One should place this
file in the `site-local` subdirectory and specify the paths by means
of `site-local/Kconfig`.

Change-Id: I86ac2a6176947f12194bec6b63bedd7db79820a0
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54761
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>

src/soc/intel/baytrail/Kconfig

@@ -155,9 +155,4 @@ config VGA_BIOS_ID
 	depends on VGA_BIOS
 	default "8086,0f31"
 
-config VGA_BIOS_FILE
-	string
-	depends on VGA_BIOS
-	default "pci8086,0f31.rom"
-
 endif