stand: Use c99 structure initialization for md device

Use c99 structure init for devsw.

Sponsored by:		Netflix

stand/common/md.c

@@ -66,15 +66,14 @@ static int md_close(struct open_file *);
 static int md_print(int);
 
 struct devsw md_dev = {
-	"md",
-	DEVT_DISK,
-	md_init,
-	md_strategy,
-	md_open,
-	md_close,
-	noioctl,
-	md_print,
-	NULL
+	.dv_name = "md",
+	.dv_type = DEVT_DISK,
+	.dv_init = md_init,
+	.dv_strategy = md_strategy,
+	.dv_open = md_open,
+	.dv_close = md_close,
+	.dv_ioctl = noioctl,
+	.dv_print = md_print,
 };
 
 static int