mfd: syscon: Fix null pointer dereference in of_syscon_register()

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

Fixes: e15d7f2 ("mfd: syscon: Use a unique name with regmap_config")
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20231204092443.2462115-1-chentao@kylinos.cn
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/mfd/syscon.c

@@ -105,6 +105,10 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 	}
 
 	syscon_config.name = kasprintf(GFP_KERNEL, "%pOFn@%pa", np, &res.start);
+	if (!syscon_config.name) {
+		ret = -ENOMEM;
+		goto err_regmap;
+	}
 	syscon_config.reg_stride = reg_io_width;
 	syscon_config.val_bits = reg_io_width * 8;
 	syscon_config.max_register = resource_size(&res) - reg_io_width;