Add timeout to i8042 driver.

Not all amd64-based PCs have functional i8042 HW (e.g. Apple products).
Because the i8042 driver busy-polls the "ready" status, this results in
performance reduction on these systems, as the device is never ready and
100% of CPU cycles are wasted checking this over and over. This commit adds
a 100 millisecond timeout the first time the device is polled, if the
timeout is reached the driver aborts.

uspace/drv/char/i8042/i8042.c

@@ -46,6 +46,7 @@
 #include <str_error.h>
 #include <inttypes.h>
 #include <io/chardev_srv.h>
+#include <time.h>
 
 #include "i8042.h"
 
@@ -113,9 +114,25 @@ static const irq_cmd_t i8042_cmds[] = {
 /** Wait until it is safe to write to the device. */
 static void wait_ready(i8042_t *dev)
 {
+	static bool first_time = true;
 	assert(dev);
-	while (pio_read_8(&dev->regs->status) & i8042_INPUT_FULL)
-		;
+
+	struct timespec cur_time, start_time;
+	if(first_time) getuptime(&start_time);
+	while (pio_read_8(&dev->regs->status) & i8042_INPUT_FULL) {
+		if (first_time) {
+			nsec_t time_diff;
+
+			getuptime(&cur_time);
+			time_diff = ts_sub_diff(&cur_time, &start_time);
+			if (time_diff > 100*1000*((nsec_t)1000)) {
+				log_msg(LOG_DEFAULT, LVL_ERROR,
+					"Timed out waiting for device ready.");
+				abort();
+			}
+		}
+	}
+	first_time = false;
 }
 
 /** Interrupt handler routine.