drivers/rtc/rtc-coh901331.c: use devm allocation

Allocate memory, region, remap and irq for device state using devm_*
helpers to simplify memory accounting.

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>