s390: always inline disabled_wait

disabled_wait uses _THIS_IP_ and assumes that compiler would inline it.
Make sure this assumption is always correct by utilizing __always_inline.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/processor.h

@@ -310,7 +310,7 @@ void enabled_wait(void);
 /*
  * Function to drop a processor into disabled wait state
  */
-static inline void __noreturn disabled_wait(void)
+static __always_inline void __noreturn disabled_wait(void)
 {
 	psw_t psw;