virt: vbox: Sanity-check parameter types for hgcm-calls coming from userspace

Userspace can make host function calls, called hgcm-calls through the
/dev/vboxguest device.

In this case we should not accept all hgcm-function-parameter-types, some
are only valid for in kernel calls.

This commit adds proper hgcm-function-parameter-type validation to the
ioctl for doing a hgcm-call from userspace.

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>