cifs: fix reconnect on smb3 mount types

cifs.ko defines two file system types: cifs & smb3, and
__cifs_get_super() was not including smb3 file system type when
looking up superblocks, therefore failing to reconnect tcons in
cifs_tree_connect().

Fix this by calling iterate_supers_type() on both file system types.

Link: https://lore.kernel.org/r/CAFrh3J9soC36+BVuwHB=g9z_KB5Og2+p2_W+BBoBOZveErz14w@mail.gmail.com
Cc: stable@vger.kernel.org
Tested-by: Satadru Pramanik <satadru@gmail.com>
Reported-by: Satadru Pramanik <satadru@gmail.com>
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>