ext4: don't update the superblock in ext4_statfs()

ext4: don't update the superblock in ext4_statfs()

commit ac08ad3e85d2b01f4fe1b75da10b5db09adbbf00 updated ext4_statfs()
to update the on-disk superblock counters, but modified this buffer
directly without any journaling of the change.  This is one of the
accesses that was causing the crc errors in journal replay as seen in
kernel.org bugzilla #14354.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org