f2fs: add new idle interval timing for discard and gc paths

This helps to control the frequency of submission of discard and
GC requests independently, based on the need.

Suggested-by: Chao Yu <[email protected]>
Signed-off-by: Sahitya Tummala <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
6 files changed