s390/irqflags: always inline arch irqflags functions

All s390 irqflags functions are very small and should be always inlined.
Therefore mark them __always_inline. This also allows to get rid of the
rather odd notrace attribute for these small functions, which was only
added to prevent tracing iff any of these functions would not be inlined.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>