perf test: Fix test case 81 ("perf record tests") on s390x

perf test: Fix test case 81 ("perf record tests") on s390x

perf test -F 81 ("perf record tests") -v fails on s390x on the
linux-next branch.

The test case is x86 specific can not be executed on s390x.  The test
case depends on x86 register names such as:

  ... | egrep -q 'available registers: AX BX CX DX ....'

Skip this test case on s390x.

Output before:

  # perf test -F 81
  81: perf record tests                       : FAILED!
  #

Output after:

  # perf test -F 81
  81: perf record tests                       : Skip
  #

Fixes: 2aa69197861cce25 ("perf test: Add basic perf record tests")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20220428122821.3652015-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>