Change i.MX21 host driver default USB Interrupt Transfer polling interval to 1ms

Prevent the host from being set to poll every frame as this causes excessive polling resulting in excessive EMC emissions
Fixes torvalds#114

Author: gthouret

Diff for: drivers/usb/host/imx21-hcd.c

@@ -909,7 +909,8 @@ static void schedule_nonisoc_etd(struct imx21 *imx21, struct urb *urb)
 	u8 dir;
 	u8 bufround;
 	u8 datatoggle;
-	u8 interval = 0;
+	/* Default polling interval of 1ms */
+	u8 interval = 1;
 	u8 relpolpos = 0;
 
 	if (etd_num < 0) {
@@ -972,7 +973,8 @@ static void schedule_nonisoc_etd(struct imx21 *imx21, struct urb *urb)
 	etd->len = count;
 
 	if (usb_pipeint(pipe)) {
-		interval = urb->interval;
+		/* Guard to prevent against excessive polling */
+		interval = (urb->interval == 0) ? 1 : urb->interval;
 		relpolpos = (readl(imx21->regs + USBH_FRMNUB) + 1) & 0xff;
 	}