drm/i915: Simplify intel_gpu_reset

Replaced ever growing switch for gen version with chained conditionals.
Futre gen's only need to add a new one if they require something different.
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Robert Beckett <robert.beckett@intel.com>
[danvet: Picked from internal tree and white-wash commit message.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_uncore.c

@@ -1154,18 +1154,16 @@ static int gen6_do_reset(struct drm_device *dev)
 
 int intel_gpu_reset(struct drm_device *dev)
 {
-	switch (INTEL_INFO(dev)->gen) {
-	case 8:
-	case 7:
-	case 6: return gen6_do_reset(dev);
-	case 5: return ironlake_do_reset(dev);
-	case 4:
-		if (IS_G4X(dev))
+	if (INTEL_INFO(dev)->gen >= 6)
+		return gen6_do_reset(dev);
+	else if (IS_GEN5(dev))
+		return ironlake_do_reset(dev);
+	else if (IS_G4X(dev))
 		return g4x_do_reset(dev);
-		else
+	else if (IS_GEN4(dev))
 		return i965_do_reset(dev);
-	default: return -ENODEV;
-	}
+	else
+		return -ENODEV;
 }
 
 void intel_uncore_check_errors(struct drm_device *dev)