fizz: Increase frequency/loudness of dev screen buzzer

According to spec, peak volume of buzzer is 2.7kHz for the
buzzer.  Increasing buzzer frequency to reflect that.

BUG=b:65981151
BRANCH=None
TEST=reboot with gbb_flags set to 0.  Ensure beep volume
     loud enough.

Change-Id: Ic9a20d8727a3518b6daee5490bb93ed3a145d0c3
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/679600Reviewed-by: Furquan Shaikh <furquan@chromium.org>

src/drivers/sound/gpio_edge_buzzer.c

@@ -26,10 +26,11 @@ static int buzzer_play(SoundOps *me, uint32_t msec, uint32_t frequency)
 	if (!frequency)
 		return -1;
 
+	/* Using frequency ~2.7kHz, which is peak loudness */
 	start = timer_us(0);
 	while (timer_us(start)/1000 < msec) {
 		buzzer->gpio->set(buzzer->gpio, ++i & 1);
-		mdelay(1);
+		udelay(185);
 	}
 	buzzer->gpio->set(buzzer->gpio, 0);