drm/i915: Replace some negative Gen checks

Instead of INTEL_GEN != x use !IS_GENx for more optimisation
opportunities.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180208130606.15556-16-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/20180209215847.6660-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_pm.c

@@ -7554,7 +7554,7 @@ unsigned long i915_chipset_val(struct drm_i915_private *dev_priv)
 {
 	unsigned long val;
 
-	if (INTEL_GEN(dev_priv) != 5)
+	if (!IS_GEN5(dev_priv))
 		return 0;
 
 	spin_lock_irq(&mchdev_lock);
@@ -7638,7 +7638,7 @@ static void __i915_update_gfx_val(struct drm_i915_private *dev_priv)
 
 void i915_update_gfx_val(struct drm_i915_private *dev_priv)
 {
-	if (INTEL_GEN(dev_priv) != 5)
+	if (!IS_GEN5(dev_priv))
 		return;
 
 	spin_lock_irq(&mchdev_lock);
@@ -7689,7 +7689,7 @@ unsigned long i915_gfx_val(struct drm_i915_private *dev_priv)
 {
 	unsigned long val;
 
-	if (INTEL_GEN(dev_priv) != 5)
+	if (!IS_GEN5(dev_priv))
 		return 0;
 
 	spin_lock_irq(&mchdev_lock);