[PATCH] ebcdic do_kdsk_ioctl off-by-one

Add a missing return check from strnlen_user and fixes a off-by-one when
terminating the string with zero.

Signed-off-by: Davi Arnaut <davi.arnaut@gmail.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>