rtc: rtc interfaces don't use class_device

This patch removes class_device from the programming interface that the RTC
framework exposes to the rest of the kernel.  Now an rtc_device is passed,
which is more type-safe and streamlines all the relevant code.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
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>