rtc-rs5c313.c: add error handling to avoid hardware hangup

Add error processing.  Hanging up by an infinite loop is evaded.

Signed-off-by: kogiidena <kogiidena@eggplant.ddo.jp>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>