rtc: pcf50633: fix month off-by-one error

The PCF50633 stores a month value of 1-12, but the kernel wants 0-11.

Signed-off-by: Rask Ingemann Lambertsen <rask@sygehus.dk>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Balaji Rao <balajirrao@openmoko.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>