drm/i915: Bump HDMI min port clock to 25 MHz

Increase the HDMI port minimum port clock from 20 to 25 MHz. This is
is the minimum listed in the DVI/HDMI specs, and it's also the
documented minimum DPLL frequency for most of our platforms.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-and-tested-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1175,7 +1175,7 @@ intel_hdmi_mode_valid(struct drm_connector *connector,
 	if (clock > hdmi_portclock_limit(intel_attached_hdmi(connector),
 					 true))
 		return MODE_CLOCK_HIGH;
-	if (clock < 20000)
+	if (clock < 25000)
 		return MODE_CLOCK_LOW;
 
 	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)