Revert "UBUNTU: [Config] Remove CONFIG_CIFS_POSIX=y"

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>

debian.master/config/config.common.ubuntu

@@ -1210,6 +1210,7 @@ CONFIG_CIFS_DEBUG=y
 # CONFIG_CIFS_DEBUG2 is not set
 CONFIG_CIFS_DFS_UPCALL=y
 CONFIG_CIFS_FSCACHE=y
+CONFIG_CIFS_POSIX=y
 CONFIG_CIFS_SMB2=y
 CONFIG_CIFS_SMB311=y
 CONFIG_CIFS_STATS=y