package/freerdp: do not forcibly depend on X.Org

It is possible to build the libfreerdp standalone, without X.Org.
Having a libfreerdp will be usefull for the weston RDP compositor.

So, only select the strictly required X.Org library if X.Org is enabled,
and only build with Xcursor if it is enabled. Drop dependency on other
X.Org libraries, as they are not strictly required (or get pulled as
dependencies of the mandatory libXext).

Re-order the menuconfig, as freerdp is no longer an X-only application.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>