chromeos chipsets: select RTC usage

Since RTC is now a Kconfig ensure RTC is selected on the
x86 chipsets which are in Chrome OS devices. This allows
the eventlog to have proper timestamps instead of all
zeros.

BUG=chrome-os-partner:55993

Change-Id: I24ae7d9b3bf43a5791d4dc04aae018ce17fda72b
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16086
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/baytrail/Kconfig

@@ -26,6 +26,7 @@ config CPU_SPECIFIC_OPTIONS
 	select PCIEXP_ASPM
 	select PCIEXP_COMMON_CLOCK
 	select REG_SCRIPT
+	select RTC
 	select SMM_TSEG
 	select SMP
 	select SPI_FLASH