firmware: Use PTR_ERR_OR_ZERO()

Fix ptr_ret.cocci warnings:
drivers/firmware/efi/efi.c:610:8-14: WARNING: PTR_ERR_OR_ZERO can be used

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci
Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

drivers/firmware/qemu_fw_cfg.c

@@ -694,10 +694,8 @@ static int fw_cfg_cmdline_set(const char *arg, const struct kernel_param *kp)
 	 */
 	fw_cfg_cmdline_dev = platform_device_register_simple("fw_cfg",
 					PLATFORM_DEVID_NONE, res, processed);
-	if (IS_ERR(fw_cfg_cmdline_dev))
-		return PTR_ERR(fw_cfg_cmdline_dev);
 
-	return 0;
+	return PTR_ERR_OR_ZERO(fw_cfg_cmdline_dev);
 }
 
 static int fw_cfg_cmdline_get(char *buf, const struct kernel_param *kp)