drm/rockchip: vop: Don't reject empty modesets

So that when DRM_IOCTL_MODE_SETCRTC is called without a FB nor mode, the
CRTC gets disabled.
Signed-off-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Link: http://lkml.kernel.org/g/CAAObsKAv+05ih5U+=4kic_NsjGMhfxYheHR8xXXmacZs+p5SHw@mail.gmail.com

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -907,9 +907,6 @@ static bool vop_crtc_mode_fixup(struct drm_crtc *crtc,
 {
 	struct vop *vop = to_vop(crtc);
 
-	if (adjusted_mode->htotal == 0 || adjusted_mode->vtotal == 0)
-		return false;
-
 	adjusted_mode->clock =
 		clk_round_rate(vop->dclk, mode->clock * 1000) / 1000;