drm/i915/skl: i915_swizzle_info gen9 fix

Fix ARB_MODE register read for gen >= 8 in i915_swizzle_info
Reviewed-by: NThomas Wood <thomas.wood@intel.com>
Signed-off-by: NRobert Beckett <robert.beckett@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1986,7 +1986,7 @@ static int i915_swizzle_info(struct seq_file *m, void *data)
 			   I915_READ(MAD_DIMM_C2));
 		seq_printf(m, "TILECTL = 0x%08x\n",
 			   I915_READ(TILECTL));
-		if (IS_GEN8(dev))
+		if (INTEL_INFO(dev)->gen >= 8)
 			seq_printf(m, "GAMTARBMODE = 0x%08x\n",
 				   I915_READ(GAMTARBMODE));
 		else