fs/9p: don't set SB_NOATIME by default

fs/9p: don't set SB_NOATIME by default

When the user uses some syscall, for example mmap(v9fs_file_mmap), it
will not update atime even if user's was set mnt_flags without
MNT_NOATIME, because v9fs defaults to settine SB_NOATIME in
v9fs_set_super.

For supporting access time updating when the user mounts with relatime,
we should not set SB_NOATIME by default.

Link: http://lkml.kernel.org/r/5AB9A377.6080906@huawei.com
Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>