[CIFS] Fix build warning

Fix build warning in Shirish's recent SMB3 signing patch
which occurs when SMB2 support is disabled in Kconfig.

fs/built-in.o: In function `cifs_setup_session':
>> (.text+0xa1767): undefined reference to `generate_smb3signingkey'

Pointed out by: automated 0-DAY kernel build testing backend
Intel Open Source Technology Center

CC: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

diff --cc fs/cifs/cifsglob.h
Simple merge

diff --cc fs/cifs/cifsproto.h
Simple merge

diff --cc fs/cifs/connect.c
Simple merge

diff --cc fs/cifs/smb2ops.c
Simple merge

diff --cc fs/cifs/smb2transport.c
Simple merge