macintosh/macio-adb: check the return value of ioremap()

The function ioremap() in macio_init() can fail, so its return value
should be checked.

Fixes: 36874579 ("[PATCH] powerpc: macio-adb build fix")
Reported-by: Hacash Robot <hacashRobot@santino.com>
Signed-off-by: Xie Shaowen <studentxswpy@163.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220802074148.3213659-1-studentxswpy@163.com

drivers/macintosh/macio-adb.c

@@ -108,6 +108,10 @@ int macio_init(void)
 		return -ENXIO;
 	}
 	adb = ioremap(r.start, sizeof(struct adb_regs));
+	if (!adb) {
+		of_node_put(adbs);
+		return -ENOMEM;
+	}
 
 	out_8(&adb->ctrl.r, 0);
 	out_8(&adb->intr.r, 0);