arm: imx9: Correct imx9_probe_mu prototype

Since the event callback imx9_probe_mu is re-defined, update
its prototype.

Signed-off-by: Ye Li <ye.li@nxp.com>
diff --git a/board/freescale/imx93_evk/spl.c b/board/freescale/imx93_evk/spl.c
index 2fd5559..7331a20 100644
--- a/board/freescale/imx93_evk/spl.c
+++ b/board/freescale/imx93_evk/spl.c
@@ -116,7 +116,7 @@
 
 	preloader_console_init();
 
-	ret = imx9_probe_mu(NULL, NULL);
+	ret = imx9_probe_mu();
 	if (ret) {
 		printf("Fail to init Sentinel API\n");
 	} else {