f2fs: add tracepoint for f2fs_gc

commit c56f16dab0dfc8a37bc6133f2c2a02ffb873648b upstream.

This patch adds tracepoint for f2fs_gc.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Git-commit: 6929c542
Git-repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>