Ensure PERF_IP_FLAG_ASYNC is set always for asynchronous branches (i.e.
interrupts etc).

Fixes: 90e457f7 ("perf tools: Add Intel PT support")
Cc: stable@vger.kernel.org
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20230928072953.19369-1-adrian.hunter@intel.comSigned-off-by: Namhyung Kim <namhyung@kernel.org>