drm/i915: Simplify gem stolen initialization.

Let's take usage of IS_LP to simplify the gem stolen
initialization as suggest by Tvrtko.

Also assume that all new LP platforms follows the chv+
and others bdw+.

v2: Remove the wrong commit message about bxt and glk. (Ander)

Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1482174347-24911-1-git-send-email-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -454,13 +454,12 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
 					 &reserved_size);
 		break;
 	default:
-		if (IS_BROADWELL(dev_priv) ||
-		    IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))
-			bdw_get_stolen_reserved(dev_priv, &reserved_base,
+		if (IS_LP(dev_priv))
+			chv_get_stolen_reserved(dev_priv, &reserved_base,
 						&reserved_size);
 		else
-			chv_get_stolen_reserved(dev_priv, &reserved_base,
-						 &reserved_size);
+			bdw_get_stolen_reserved(dev_priv, &reserved_base,
+						&reserved_size);
 		break;
 	}