lib: utils/i2c: Use fdt_driver for initialization

The i2c driver subsystem does not need any extra data, so it can use
`struct fdt_driver` directly. It always initializes the driver for a
specific DT node.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/utils/i2c/fdt_i2c_dw.c

@@ -49,7 +49,7 @@ static const struct fdt_match fdt_dw_i2c_match[] = {
 	{ },
 };
 
-struct fdt_i2c_adapter fdt_i2c_adapter_dw = {
+const struct fdt_driver fdt_i2c_adapter_dw = {
 	.match_table = fdt_dw_i2c_match,
 	.init = fdt_dw_i2c_init,
 };