perf/bpf: Mark perf_event_set_bpf_handler() and perf_event_free_bpf_handler() as inline too

They can be unused with certain Kconfig variations:

  kernel/events/core.c:9622:13: warning: ‘perf_event_free_bpf_handler’ defined but not used [-Wunused-function]
  kernel/events/core.c:9586:12: warning: ‘perf_event_set_bpf_handler’ defined but not used [-Wunused-function]

Since they are both single-use, mark them inline.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Kyle Huey <khuey@kylehuey.com>