drivers/rtc/rtc-max77686.c: fix incorrect return value on error

'ret' was not initialized to error code before returning. While
at it also remove some redundant code and cleanup.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Chiwoong Byun <woong.byun@samsung.com>
Cc: Jonghwa Lee <jonghwa3.lee@samsung.com>
Cc: Laxman dewangan <ldewangan@nvidia.com>
Cc: Venu Byravarasu <vbyravarasu@nvidia.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>