Read back the ack from keyboard controller after sending command
and data to set leds - otherwise controller can hang.

Reference: /n/sources/patch/applied/setleds-nohang
Date: Tue Jun 14 11:40:59 CES 2011
Signed-off-by: miller@hamnavoe.com

--- /sys/src/9/pc/kbd.c	Tue Jun 14 11:38:40 2011
+++ /sys/src/9/pc/kbd.c	Tue Jun 14 11:38:36 2011
@@ -349,8 +349,12 @@
 	ilock(&i8042lock);
 	outready();
 	outb(Data, 0xed);		/* `reset keyboard lock states' */
+	if(inready() == 0)
+		inb(Data);
 	outready();
 	outb(Data, leds);
+	if(inready() == 0)
+		inb(Data);
 	outready();
 	iunlock(&i8042lock);
 }