CHROMIUM: dark resume: Add rtc-cmos wake source functionality

CHROMIUM: dark resume: Add rtc-cmos wake source functionality

Add the proper callbacks and structs to rtc cmos such that user space can make
the rtc cmos a wake source for dark resume. The callback function checks a
register of the rtc cmos to see if an interrupt happened. Ideally this should
instead make an ACPI function call that checks what the wake source was and see
if that's the RTC, but we don't have that implemented yet.

BUG=chrome-os-partner:9812
TEST=suspend system, watch dark resumes

Change-Id: I2232b0247e0cf59394da7c530d9e63a6e70bbd17
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/42924
Reviewed-by: Olof Johansson <olofj@chromium.org>
Reviewed-by: Sameer Nanda <snanda@chromium.org>