gfs2: don't worry about I_DIRTY_TIME in gfs2_fsync()

The I_DIRTY_TIME flag is primary used within the VFS, and there's no
reason for ->fsync() implementations to do anything with it.  This is
because when !datasync, the VFS will expire dirty timestamps before
calling ->fsync().  (See vfs_fsync_range().)  This turns I_DIRTY_TIME
into I_DIRTY_SYNC.

Therefore, change gfs2_fsync() to not check for I_DIRTY_TIME.

Link: https://lore.kernel.org/r/20210112190253.64307-11-ebiggers@kernel.org


Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>