[main] Match "starting execution" and "initialising devices" message style

Add a trailing "ok" to the "initialising devices message", to match
the visual style of the "ok" now added to the "starting execution"
message.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/main.c

 	struct image *image;
 
 	/* Some devices take an unreasonably long time to initialise */
-	printf ( PRODUCT_SHORT_NAME " initialising devices...\n" );
-
+	printf ( PRODUCT_SHORT_NAME " initialising devices..." );
 	initialise();
 	startup();
+	printf ( "ok\n" );
 
 	/*
 	 * Print welcome banner