rtc: pl031: encapsulate per-vendor ops

Move the per-vendor operations for this RTC into a encapsulating struct so
we can have more per-vendor variables than just the ops.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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>