CIFS: Fix some return values in case of error in 'crypt_message'

'rc' is known to be 0 at this point. So if 'init_sg' or 'kzalloc' fails, we
should return -ENOMEM instead.

Also remove a useless 'rc' in a debug message as it is meaningless here.

Fixes: 026e93dc ("CIFS: Encrypt SMB3 requests before sending")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <smfrench@gmail.com>
CC: Stable <stable@vger.kernel.org>