drm/i915: Fix g4x+ sprite dotclock limit for upscaling

Even if we're not doing downscaling we should account for
some of the extra dotclock limitations for g4x+ sprites. In
particular we must never exceed the 90% rule, and with RGB
that limits actually drops to 80%.

So instead of bailing out when upscaling let's clamp the
scaling factor appropriately and go through the rest of
calculation normally. By luck we already did the full
calculations for the 1:1 case.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200206201204.31704-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_sprite.c

@@ -1626,8 +1626,7 @@ static int g4x_sprite_min_cdclk(const struct intel_crtc_state *crtc_state,
 	hscale = drm_rect_calc_hscale(&plane_state->uapi.src,
 				      &plane_state->uapi.dst,
 				      0, INT_MAX);
-	if (hscale < 0x10000)
-		return pixel_rate;
+	hscale = max(hscale, 0x10000u);
 
 	/* Decimation steps at 2x,4x,8x,16x */
 	decimate = ilog2(hscale >> 16);