ext4: add a new spinlock i_raw_lock to protect the ext4's raw inode

To avoid potential data races, use a spinlock which protects the raw
(on-disk) inode.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/inode.c
Simple merge

diff --cc fs/ext4/super.c
Simple merge