UPSTREAM: f2fs: atomic: fix to forbid dio in atomic_file

atomic write can only be used via buffered IO, let's fail direct IO on
atomic_file and return -EOPNOTSUPP.

Change-Id: I263aaa3764cc912c5bd0a5edd2de7d869ff52eab
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Bug: 452794646
(cherry picked from commit b2c160f4)
Change-Id: Iccdcb32caf3eaa322439c32563576772bd4d4af6
Signed-off-by: Joanne Chang <joannechien@google.com>