s390/kvm_stat: correct sys_perf_event_open syscall number

s390/kvm_stat: correct sys_perf_event_open syscall number

Correct sys_perf_event_open syscall number for s390 architecture
   - the hardcoded syscall number 298 is for x86 but should
     be different for other architectures.
     In case we figure out via /proc/cpuinfo that we are running
     on s390 the appropriate syscall number is used from map
     syscall_numbers; other architectures can extend this.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>