UPSTREAM: fs: expose LOOKUP_CACHED through openat2() RESOLVE_CACHED

[ Upstream commit 99668f61 ]

Now that we support non-blocking path resolution internally, expose it
via openat2() in the struct open_how ->resolve flags. This allows
applications using openat2() to limit path resolution to the extent that
it is already cached.

If the lookup cannot be satisfied in a non-blocking manner, openat2(2)
will return -1/-EAGAIN.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Change-Id: Iddb58268e0a2b8adfc54e56192da43dda1868d8c
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 5683caa7)
Bug: 268174392
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>