perf test: Disable test cases 19 and 20 on s390x

perf test: Disable test cases 19 and 20 on s390x

The s390x CPU sampling and measurement facilities do not support perf
events of type PERF_TYPE_BREAKPOINT. The test cases are executed and
fail with -ENOENT due to missing hardware support.

Disable the execution of both test cases based on a
platform check. This is the same approach as done for
PowerPC.

Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
LPU-Reference: 20171123074623.20817-1-tmricht@linux.vnet.ibm.com
Link: https://lkml.kernel.org/n/tip-uqvoy6a1tsu8jddo5jjg4h85@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>