Revert "f2fs: use percpu_rw_semaphore"

LKP reported -36.3% regression of fsmark.files_per_sec due to this patch.
I've confirmed that fxmark [1] has also slight regression for DWAL.

[1] https://github.com/sslab-gatech/fxmark

This reverts commit ec795418c41850056feb956534edf059dc1155d4.
3 files changed