rtc: fix ds1388 time corruption

The ds1307 driver misreads the ds1388 registers when checking for 12 or 24
hour mode.  Instead of checking the hour register it reads the minute
register.  Therefore the driver thinks minutes >= 40 has the 12HR bit set
and resets the minute register by zeroing the high bits.  This results in
minutes are reset to 0-9, jumping back in time 40 or 50 minutes.  The time
jump is also written back to the RTC.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Cc: Wan ZongShun <mcuos.com@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>