mb/google/rex: Allow to show early splash screen using GFX PEIM

This patch chooses to show the early splash screen which is an
OEM feature. The current implementation is relying on the Intel
FSP GFX PEIM to perform the display initialization.

Having this feature allows the platform to show the user notification
with 500ms since boot compared to traditional scenarios where first
user notification is coming from kernel (typically ~3sec+ after cpu
reset). Eventually this feature will help to improve the user
experience while booting Intel SoC platform based chromeos devices.

BUG=b:284799726
TEST=Able to see the early splash screen on google/rex.

Change-Id: I399ddb6618e774302200e8a87629647ba070d080
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76361
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/rex/Kconfig

@@ -35,6 +35,7 @@ config BOARD_GOOGLE_BASEBOARD_REX
 	select DRIVERS_INTEL_PMC
 	select DRIVERS_GENERIC_GPIO_KEYS
 	select DRIVERS_WWAN_FM350GL
+	select HAVE_FSP_LOGO_SUPPORT if RUN_FSP_GOP
 	select HAVE_SLP_S0_GATE
 	select MAINBOARD_HAS_CHROMEOS
 	select MEMORY_SOLDERDOWN