cifs: fix indentation in make menuconfig options

The options that are displayed for the smb3.1.1/cifs client
in "make menuconfig" are confusing because some of them are
not indented making them not appear to be related to cifs.ko
Fix that by adding an if/endif (similar to what ceph and 9pm did)
if fs/cifs/Kconfig

Suggested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>