perf ftrace: Use CAP_SYS_ADMIN instead of euid==0

The kernel requires CAP_SYS_ADMIN instead of euid==0 to mount debugfs
for ftrace.  Make perf do the same.

Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/bd8763b72ed4d58d0b42d44fbc7eb474d32e53a3.1565188228.git.ilubashe@akamai.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>