rtc: rtc-dm355evm driver

Simple RTC driver for the MSP430 firmware on the DM355 EVM board.  Other
than not supporting atomic reads/writes of all four bytes, this is
reasonable as a basic no-alarm RTC.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Acked-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>