cifs: make CIFS depend on CRYPTO_ECB

When CONFIG_CRYPTO_ECB is not set, trying to mount a CIFS share with NTLM
security resulted in mount failure with the following error:
   "CIFS VFS: could not allocate des crypto API"

Seems like a leftover from commit 43988d7.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
CC: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>