drm/v3d: Skip debugfs dumping GCA on platforms without GCA.

Fixes an oops reading this debugfs entry on BCM7278.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180928232126.4332-4-eric@anholt.net
Fixes: 57692c9 ("drm/v3d: Introduce a new DRM driver for Broadcom V3D V3.x+")
Cc: <stable@vger.kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/gpu/drm/v3d/v3d_debugfs.c

@@ -71,10 +71,13 @@ static int v3d_v3d_debugfs_regs(struct seq_file *m, void *unused)
 			   V3D_READ(v3d_hub_reg_defs[i].reg));
 	}
 
-	for (i = 0; i < ARRAY_SIZE(v3d_gca_reg_defs); i++) {
-		seq_printf(m, "%s (0x%04x): 0x%08x\n",
-			   v3d_gca_reg_defs[i].name, v3d_gca_reg_defs[i].reg,
-			   V3D_GCA_READ(v3d_gca_reg_defs[i].reg));
+	if (v3d->ver < 41) {
+		for (i = 0; i < ARRAY_SIZE(v3d_gca_reg_defs); i++) {
+			seq_printf(m, "%s (0x%04x): 0x%08x\n",
+				   v3d_gca_reg_defs[i].name,
+				   v3d_gca_reg_defs[i].reg,
+				   V3D_GCA_READ(v3d_gca_reg_defs[i].reg));
+		}
 	}
 
 	for (core = 0; core < v3d->cores; core++) {