rtc: class driver for ppc_md RTC functions

This hooks up the platform-specific [gs]et_rtc_time functions so that
kernels using CONFIG_RTC_CLASS have RTC support on most PowerPC platforms.

A new driver, and one which we've been shipping in Fedora for a while
already, since otherwise RTC support breaks.

[akpm@linux-foundation.org: fix Kconfig indenting]
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: David Brownell <david-b@pacbell.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>