cifs: fix check of dfs interlinks

cifs: fix check of dfs interlinks

BugLink: https://bugs.launchpad.net/bugs/1938340
[ Upstream commit 889c2a700799f3b6f82210925e1faf4a9b833c4a ]

Interlink is a special type of DFS link that resolves to a different
DFS domain-based namespace.  To determine whether it is an interlink
or not, check if ReferralServers and StorageServers bits are set to 1
and 0 respectively in ReferralHeaderFlags, as specified in MS-DFSC
3.1.5.4.5 Determining Whether a Referral Response is an Interlink.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>