[main] Defer "initialising devices" message until initialising devices

Allow the "initialising devices" message to show up on consoles which
require initialisation, by deferring it until after initialise() has
completed.

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

src/core/main.c

  */
 __asmcall int main ( void ) {
 
+	/* Perform one-time-only initialisation (e.g. heap) */
+	initialise();
+
 	/* Some devices take an unreasonably long time to initialise */
 	printf ( PRODUCT_SHORT_NAME " initialising devices..." );
-	initialise();
 	startup();
 	printf ( "ok\n" );