Revert "f2fs: use percpu_counter for # of dirty pages in inode"

commit 204706c7accfabb67b97eef9f9a28361b6201199 upstream.

This reverts commit 1beba1b3a953107c3ff5448ab4e4297db4619c76.

The perpcu_counter doesn't provide atomicity in single core and consume more
DRAM. That incurs fs_mark test failure due to ENOMEM.

Cc: stable@vger.kernel.org # 4.7+
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>