drivers/rtc/rtc-efi.c: add missing module alias

Without proper alias kernel module is not loaded for rtc-efi driver.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Cc: dann frazier <dannf@dannf.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>