drm/vmwgfx: Add gui_x/y to vmw_connector_state

As gui_x/y positioning is display unit is protected by
requested_layout_mutex adding vmw_connector_state copy of the same and
modeset commit will refer the state copy to sync with modeset_check
state.

v2: Tested with CONFIG_PROVE_LOCKING enabled.

Signed-off-by: Deepak Rawat <drawat@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>