s390/atomic: use 'unsigned int' instead of 'unsigned long' for atomic_*_mask()

The type of 'v->counter' is always 'int', and related inline assembly
code also process 'int', so use 'unsigned int' instead of 'unsigned
long' for the 'mask'.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>