Use menuconfig objects: RTC

Change Kconfig objects from "menu, config" into "menuconfig" so that the
user can disable the whole feature without having to enter the menu first.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Cc: David Brownell <david-b@pacbell.net>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>