drivers/rtc/rtc-s35390a.c: add wakealarm support for rtc-s35390A rtc chip

Add basic get/set alarm support for the Seiko Instruments S-35390A.  The
chip is used on the QNAP TS-219P+ NAS device.

Signed-off-by: Michael Langer <michael.brainbug.langer@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>