x86: Allow video-BIOS code to be built for SPL

With qemu-x86_64 we need to run the video BIOS while in 32-bit mode, i.e.
SPL. Add a Kconfig option for this, adjust the Makefile rules and use
CONFIG_IS_ENABLED() where needed.

Change-Id: I5d7962e5f9d12c176625cd77882e45ababdb590a
Signed-off-by: Simon Glass <sjg@chromium.org>
3 files changed