drm/i915: Avoid using dev_priv->info.gen directly.

Let's stop this usage before it spreads so much.

1. This check is not part of usual searches happening when adding
new platform.
2. There is already a duplication here with INTEL_INFO(dev_priv)->gen
and INTEL_GEN(dev_priv).

So let's please avoid yet another way.

Cc: Lyude <cpaul@redhat.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170926211346.12009-1-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -9310,11 +9310,11 @@ static bool haswell_get_pipe_config(struct intel_crtc *crtc,
 	pipe_config->gamma_mode =
 		I915_READ(GAMMA_MODE(crtc->pipe)) & GAMMA_MODE_MODE_MASK;
 
-	if (IS_BROADWELL(dev_priv) || dev_priv->info.gen >= 9) {
+	if (IS_BROADWELL(dev_priv) || INTEL_GEN(dev_priv) >= 9) {
 		u32 tmp = I915_READ(PIPEMISC(crtc->pipe));
 		bool clrspace_yuv = tmp & PIPEMISC_OUTPUT_COLORSPACE_YUV;
 
-		if (IS_GEMINILAKE(dev_priv) || dev_priv->info.gen >= 10) {
+		if (IS_GEMINILAKE(dev_priv) || INTEL_GEN(dev_priv) >= 10) {
 			bool blend_mode_420 = tmp &
 					      PIPEMISC_YUV420_MODE_FULL_BLEND;
 
@@ -14280,7 +14280,7 @@ void intel_init_display_hooks(struct drm_i915_private *dev_priv)
 		dev_priv->display.fdi_link_train = hsw_fdi_link_train;
 	}
 
-	if (dev_priv->info.gen >= 9)
+	if (INTEL_GEN(dev_priv) >= 9)
 		dev_priv->display.update_crtcs = skl_update_crtcs;
 	else
 		dev_priv->display.update_crtcs = intel_update_crtcs;