lib: utils/ipi: Use fdt_driver for initialization

The ipi driver subsystem does not need any extra data, so it can use
`struct fdt_driver` directly. The generic fdt_ipi_init() performs a
best-effort initialization of all matching DT nodes.

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

lib/utils/ipi/fdt_ipi_plicsw.c

@@ -39,7 +39,7 @@ static const struct fdt_match ipi_plicsw_match[] = {
 	{},
 };
 
-struct fdt_ipi fdt_ipi_plicsw = {
+const struct fdt_driver fdt_ipi_plicsw = {
 	.match_table = ipi_plicsw_match,
-	.cold_init   = fdt_plicsw_cold_ipi_init,
+	.init = fdt_plicsw_cold_ipi_init,
 };