rtc-dev: Make RTC driver return ENOTTY instead of ENOIOCTLCMD

Prevent the RTC driver from returning ENOIOCTLCMD to userspace.

Signed-off-by: Thomas Hommel <thomas.hommel@gefanuc.com>
Acked-by: 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>