rtc-m48t59: add support for M48T02 and M48T59 chips

Add support for two compatible RTC:
- M48T08 which does not have alarm part,
- M48T08 which does not have alarm part and has
  only 2KB of NVRAM

These types covers all Mostek's RTC used in Sun UltraSparc workstations.

Tested on Sun Ultra60 with M48T59 RTC.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>