perf arm-spe: Correct sample flags for dummy event

The dummy event is mainly used for mmap, the TIME sample is only needed
for per-cpu case so that the perf tool can rely on the correct timing
for parsing symbols.  And the CPU sample is useless for mmap.

The BRANCH_STACK sample bit will be always reset for the dummy event in
the function evsel__config(), so don't need to repeatedly reset it for
Arm SPE specific.

So this patch only enables TIME sample for per-cpu mmap.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: James Clark <james.clark@arm.com>
Tested-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Al Grant <Al.Grant@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20210519041546.1574961-3-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>