soc/intel/baytrail: refactor rtc failure checking

In order to prepare for checking RTC failure in the early boot
paths move the rtc failure calculation to pmutil.c and add a helper
function to determine if failure occurred.

BUG=b:63054105

Change-Id: I1d90cc557225ddbba1787bf95eae0de623af487e
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/21555
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/baytrail/Makefile.inc

@@ -26,6 +26,7 @@ ramstage-y += gpio.c
 romstage-y += reset.c
 ramstage-y += reset.c
 ramstage-y += cpu.c
+romstage-y += pmutil.c
 ramstage-y += pmutil.c
 smm-y += pmutil.c
 smm-y += smihandler.c