s390/cpumf: fix semicolon.cocci warnings

arch/s390/kernel/perf_cpum_cf.c:748:2-3: Unneeded semicolon

 Remove unneeded semicolon.

Generated by: scripts/coccinelle/misc/semicolon.cocci

Fixes: a029a4ea

 ("s390/cpumf: Allow concurrent access for CPU Measurement Counter Facility")
CC: Thomas Richter <tmricht@linux.ibm.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>