cifs: Fix regression in LANMAN (LM) auth code

LANMAN response length was changed to 16 bytes instead of 24 bytes.
Revert it back to 24 bytes.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
CC: stable@kernel.org
Signed-off-by: Steve French <sfrench@us.ibm.com>