drivers/rtc/rtc-ab8500.c: add second resolution to rtc driver

Android expects the RTC to have second resolution.  On ab8540 cut2 RTC
block has a new register which allows setting seconds for wakeup alarms.

Existing registers (minutes hi, mid and low) have seen their offsets
changed. Here is the new mapping:
  * AlarmSec     (A) 0x22
  * AlarmMinLow  (M) from 0x8 to 0x23
  * AlarmMinMid  (M) from 0x9 to 0x24
  * AlarmMinHigh (M) from 0xA to 0x25

Signed-off-by: Julien Delacou <julien.delacou@stericsson.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>