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>

drivers/rtc/Kconfig

@@ -406,10 +406,13 @@ config RTC_DRV_M48T86
 	  will be called rtc-m48t86.
 
 config RTC_DRV_M48T59
-	tristate "ST M48T59"
+	tristate "ST M48T59/M48T08/M48T02"
 	help
 	  If you say Y here you will get support for the
-	  ST M48T59 RTC chip.
+	  ST M48T59 RTC chip and compatible ST M48T08 and M48T02.
+
+	  These chips are usually found in Sun SPARC and UltraSPARC
+	  workstations.
 
 	  This driver can also be built as a module, if so, the module
 	  will be called "rtc-m48t59".