drm/vmwgfx: use vmw_cmd_dx_cid_check for query commands.

Instead of calling vmw_cmd_ok, call vmw_cmd_dx_cid_check to
validate the context id for query commands.

Signed-off-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>