Since commit a2ad63da ("VFS: add FMODE_CAN_ODIRECT file flag") file
systems can just set the FMODE_CAN_ODIRECT flag at open time instead of
wiring up a dummy direct_IO method to indicate support for direct I/O.
Do that for bcachefs so that noop_direct_IO can eventually be removed.

Similar to commit b2943499 ("xfs: set FMODE_CAN_ODIRECT instead of
a dummy direct_IO method").
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>