Provide the basic "get" and "set" functionality for the Epson RX-8581 I2C
RTC.  It currently does not support the RTC's Alarm or Fixed-cycle timer.

[akpm@linux-foundation.org: need log2.h for ilog2(), remove unneeded initialisation]
Signed-off-by: NMartyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: NAlessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>