rtc: U300 COH 901 331 RTC driver v3

This adds a driver for the RTC COH 901 331 found in the ST-Ericsson U300
series mobile platforms to the RTC subsystem.  It integrates to the ARM
kernel support recently added to RMKs ARM tree and will be enabled in the
U300 defconfig in due time.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>