Revert "usb: musb: musb_host: Enable HCD_BH flag to handle urb return in bottom half"

This reverts commit 20357720.

Commit 20357720 claims throughput improvement for MSC/UVC, but I
don't see much improvement. Following are the MSC measurement using
dd on AM335x GP EVM.

with BCD_BH:    read: 14.9MB/s, write: 20.9MB/s
without BCD_BH: read: 15.2MB/s, write: 21.2MB/s

However with this commit the following regressions have been observed.

1. ASIX usb-ethernet dongle is completely broken on UDP RX.

2. Unpluging a 3G modem, which uses option driver, behind a hub causes
   console log flooding with the following message.

   option_instat_callback: error -71
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_host.c

@@ -2735,7 +2735,7 @@ static const struct hc_driver musb_hc_driver = {
 	.description		= "musb-hcd",
 	.product_desc		= "MUSB HDRC host driver",
 	.hcd_priv_size		= sizeof(struct musb *),
-	.flags			= HCD_USB2 | HCD_MEMORY | HCD_BH,
+	.flags			= HCD_USB2 | HCD_MEMORY,
 
 	/* not using irq handler or reset hooks from usbcore, since
 	 * those must be shared with peripheral code for OTG configs