s390/cpum_sf: Rework call to sf_disable()

s390/cpum_sf: Rework call to sf_disable()

Setup_pmc_cpu() function body consists of one single switch
statement with two cases PMC_INIT and PMC_RELEASE.
In both of these cases sf_disable() is invoked to turn off the
CPU Measurement sampling facility.
Move sf_disable() out of the switch statement.
No functional change.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>