port-i386/44563: boot loader prompt doesn't read keyboard input on a MacBook1,1

check for keystroke (int 16h, AH=01h) before getting keystroke (int 16h,
AH=00h), fixes bootloader keyboard input with Apple firmware, from Taylor R
Campbell

sys/arch/i386/stand/lib/pcio.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: pcio.c,v 1.28 2010/06/25 15:35:08 tsutsui Exp $	 */
+/*	$NetBSD: pcio.c,v 1.29 2011/02/14 23:47:11 jmcneill Exp $	 */
 
 /*
  * Copyright (c) 1996, 1997
@@ -271,6 +271,8 @@ getchar(void)
 	default: /* to make gcc -Wall happy... */
 	case CONSDEV_PC:
 #endif
+		while (!coniskey())
+			;
 		c = congetc();
 #ifdef CONSOLE_KEYMAP
 		{