The big win here is a shrink of runtime code size, but again there's
the usual MODULE_ALIAS_MISCDEV and sparse stuff and more traditional
coding style.

RTC driver cleanups:

    - Various "sparse" fixes
    - Reduce some pointless code duplication
    - Add a MODULE_ALIAS_MISCDEV (supports KMOD)
    - Style and other code cleanups

Object code shrinks by almost 800 bytes.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>