cifs: In Kconfig CONFIG_CIFS_POSIX needs depends on legacy (insecure cifs)

Missing a dependency.  Shouldn't show cifs posix extensions
in Kconfig if CONFIG_CIFS_ALLOW_INSECURE_DIALECTS (ie SMB1
protocol) is disabled.
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/Kconfig

@@ -133,7 +133,7 @@ config CIFS_XATTR
 
 config CIFS_POSIX
         bool "CIFS POSIX Extensions"
-        depends on CIFS_XATTR
+        depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY && CIFS_XATTR
         help
           Enabling this option will cause the cifs client to attempt to
 	  negotiate a newer dialect with servers, such as Samba 3.0.5