rtc: rtc-rs5c372: add support for Ricoh R2025S/D RTC

This adds support for the Ricoh R2025S/D series of I2C RTCs, produced by
Ricoh Japan and described at:

	http://www.ricoh.co.jp/LSI/product_rtc/2wire/r2025x/



This series has very minor deviations from the rest of the RS5C chips,
most of which have to do with the oscillator, which was abstracted away in
an earlier patch.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: David Brownell <david-b@pacbell.net>
Tested-by: Riku Voipio <riku.voipio@movial.fi>
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>