rtc: driver for Conexant Digicolor CX92755 on-chip RTC

Add driver for the RTC hardware block on the Conexant CX92755 SoC, from
the Digicolor series of SoCs.  Tested on the Equinox evaluation board for
the CX92755 chip.

[akpm@linux-foundation.org: build command arrays at compile-time]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>