drm/i915: Use INTEL_GEN everywhere

Coccinelle patch:

 @@
 identifier p;
 @@
 -INTEL_INFO(p)->gen
 +INTEL_GEN(p)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180208130606.15556-12-tvrtko.ursulin@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180209215847.6660-1-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index e702a64..78a53c8b 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -497,7 +497,7 @@ static u32 i9xx_get_backlight(struct intel_connector *connector)
 	u32 val;
 
 	val = I915_READ(BLC_PWM_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
-	if (INTEL_INFO(dev_priv)->gen < 4)
+	if (INTEL_GEN(dev_priv) < 4)
 		val >>= 1;
 
 	if (panel->backlight.combination_mode) {