BugLink: https://bugs.launchpad.net/bugs/1818813

This reverts commit 2fb90420.

The commit ("cifs: In Kconfig CONFIG_CIFS_POSIX needs depends on legacy
(insecure cifs)") that required 2fb90420 was reverted, so we need to
revert 2fb90420 as well.
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>