[S390] uaccess_mvcos: #ifdef config dependent code.

arch/s390/lib/uaccess_mvcos.c:166:
 warning: 'strnlen_user_mvcos' defined but not used
arch/s390/lib/uaccess_mvcos.c:186:
 warning: 'strncpy_from_user_mvcos' defined but not used

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>