drm/i915/gtt: Tidy up duplicate branches in gen8_gmch_probe()

Following commit f773568b ("drm/i915: nuke the duplicated stolen
discovery"), the if-else-chain for determining the GTT size is redundant
with the !chv branches all being the same.
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
References: f773568b ("drm/i915: nuke the duplicated stolen discovery")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180503212956.3948-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -3326,14 +3326,10 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
 		DRM_ERROR("Can't set DMA mask/consistent mask (%d)\n", err);
 
 	pci_read_config_word(pdev, SNB_GMCH_CTRL, &snb_gmch_ctl);
-
-	if (INTEL_GEN(dev_priv) >= 9) {
-		size = gen8_get_total_gtt_size(snb_gmch_ctl);
-	} else if (IS_CHERRYVIEW(dev_priv)) {
+	if (IS_CHERRYVIEW(dev_priv))
 		size = chv_get_total_gtt_size(snb_gmch_ctl);
-	} else {
+	else
 		size = gen8_get_total_gtt_size(snb_gmch_ctl);
-	}
 
 	ggtt->base.total = (size / sizeof(gen8_pte_t)) << PAGE_SHIFT;
 	ggtt->base.cleanup = gen6_gmch_remove;