x86: Move VGA option rom macros to Kconfig

Move X86_OPTION_ROM_FILE & X86_OPTION_ROM_ADDR to arch/x86/Kconfig
and rename them to VGA_BIOS_FILE & VGA_BIOS_ADDR which depend on
HAVE_VGA_BIOS. The new names are consistent with other x86 binary
blob options like HAVE_FSP/FSP_FILE/FSP_ADDR.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>