f2fs: trace __submit_discard_cmd

Add an even class f2fs_discard for introducing f2fs_queue_discard, then
use f2fs_{queue,issue}_discard to trace __{queue,submit}_discard_cmd.

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
2 files changed