lib/edid: Split out fill_lb_framebuffer()

Place it into new edid_fill_fb.c, and invert the logic of the Kconfig
guard (NATIVE_VGA_INIT_USE_EDID is now !NO_EDID_FILL_FB). It has to be
selected by all drivers that use MAINBOARD_DO_NATIVE_VGA_INIT but pro-
vide their own fill_lb_framebuffer() implementation.

Change-Id: I90634b835bd8e2d150b1c714328a5b2774d891bd
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/19764
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/lib/Makefile.inc

@@ -131,6 +131,9 @@ ramstage-$(CONFIG_TRACE) += trace.c
 ramstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
 ramstage-$(CONFIG_COVERAGE) += libgcov.c
 ramstage-y += edid.c
+ifneq ($(CONFIG_NO_EDID_FILL_FB),y)
+ramstage-y += edid_fill_fb.c
+endif
 ramstage-y += memrange.c
 ramstage-$(CONFIG_COOP_MULTITASKING) += thread.c
 ramstage-$(CONFIG_TIMER_QUEUE) += timer_queue.c