perf/test: fix perf ftrace test on s390

On s390 the perf test case ftrace sometimes fails as follows:

  # ./perf test ftrace
  79: perf ftrace tests    : FAILED!
  #

The failure depends on the kernel .config file. Some configurations
always work fine, some do not.  The ftrace profile test mostly fails,
because the ring buffer was not large enough, and some lines
(especially the interesting ones with nanosleep in it) where dropped.

To achieve success for all tested kernel configurations, enlarge
the buffer to store the traces completely without wrapping.
The default buffer size is too small for all kernel configurations.
Set the buffer size of for the ftrace profile test to 16 MB.

Output after:
  # ./perf test ftrace
  79: perf ftrace tests     : Ok
  #

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: agordeev@linux.ibm.com
Cc: gor@linux.ibm.com
Cc: hca@linux.ibm.com
Cc: sumanthk@linux.ibm.com
Link: https://lore.kernel.org/r/20241119064856.641446-1-tmricht@linux.ibm.com


Suggested-by: Sven Schnelle <svens@linux.ibm.com>
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>