drivers/rtc/rtc-vt8500.c: fix year field in vt8500_rtc_set_time()

The year field is incorrectly masked when setting the date.  If the year
is beyond 2099, the year field will be incorrectly updated in hardware.

This patch masks the year field correctly.

Signed-off-by: Edgar Toernig <froese@gmx.de>
Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
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>