drm/i915: Fix VBT backlight Hz to PWM conversion for PNV

Convert the MHz number coming from intel_rawclk() into Hz in
i9xx_hz_to_pwm() on PNV. Otherwise we'll get something totally
bogus as a result.

Fixes: aa17cdb4 ("drm/i915: initialize backlight max from VBT")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448893432-6978-2-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_panel.c

@@ -1343,7 +1343,7 @@ static u32 i9xx_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
 	int clock;
 
 	if (IS_PINEVIEW(dev))
-		clock = intel_hrawclk(dev);
+		clock = MHz(intel_hrawclk(dev));
 	else
 		clock = 1000 * dev_priv->display.get_display_clock_speed(dev);