Kconfig: Add choice of framebuffer mode

Rename `FRAMEBUFFER_KEEP_VESA_MODE` to `LINEAR_FRAMEBUFFER` and put
it together with new `VGA_TEXT_FRAMEBUFFER` into a choice. There are
two versions of `LINEAR_FRAMEBUFFER` that differ only in the prompt
and help text (one for `HAVE_VBE_LINEAR_FRAMEBUFFER` and one for
`HAVE_LINEAR_FRAMEBUFFER`). Due to `kconfig_lint` we have to model
that with additional symbols.

Change-Id: I9144351491a14d9bb5e650c14933b646bc83fab0
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/19804
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
14 files changed