fs/smb/client: Implement new SMB3 POSIX type

Fixes special files against current Samba.

On the Samba server:

insgesamt 20
131958 brw-r--r--  1 root  root  0, 0 15. Nov 12:04 blockdev
131965 crw-r--r--  1 root  root  1, 1 15. Nov 12:04 chardev
131966 prw-r--r--  1 samba samba    0 15. Nov 12:05 fifo
131953 -rw-rwxrw-+ 2 samba samba    4 18. Nov 11:37 file
131953 -rw-rwxrw-+ 2 samba samba    4 18. Nov 11:37 hardlink
131957 lrwxrwxrwx  1 samba samba    4 15. Nov 12:03 symlink -> file
131954 -rwxrwxr-x+ 1 samba samba    0 18. Nov 15:28 symlinkoversmb

Before:

ls: cannot access '/mnt/smb3unix/posix/blockdev': No data available
ls: cannot access '/mnt/smb3unix/posix/chardev': No data available
ls: cannot access '/mnt/smb3unix/posix/symlinkoversmb': No data available
ls: cannot access '/mnt/smb3unix/posix/fifo': No data available
ls: cannot access '/mnt/smb3unix/posix/symlink': No data available
total 16
     ? -????????? ? ?    ?     ?            ? blockdev
     ? -????????? ? ?    ?     ?            ? chardev
     ? -????????? ? ?    ?     ?            ? fifo
131953 -rw-rwxrw- 2 root samba 4 Nov 18 11:37 file
131953 -rw-rwxrw- 2 root samba 4 Nov 18 11:37 hardlink
     ? -????????? ? ?    ?     ?            ? symlink
     ? -????????? ? ?    ?     ?            ? symlinkoversmb

After:

insgesamt 21
131958 brw-r--r-- 1 root root  0, 0 15. Nov 12:04 blockdev
131965 crw-r--r-- 1 root root  1, 1 15. Nov 12:04 chardev
131966 prw-r--r-- 1 root samba    0 15. Nov 12:05 fifo
131953 -rw-rwxrw- 2 root samba    4 18. Nov 11:37 file
131953 -rw-rwxrw- 2 root samba    4 18. Nov 11:37 hardlink
131957 lrwxrwxrwx 1 root samba    4 15. Nov 12:03 symlink -> file
131954 lrwxrwxr-x 1 root samba   23 18. Nov 15:28 symlinkoversmb -> mnt/smb3unix/posix/file

Cc: stable@vger.kernel.org
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>