staging: most: fix USB babble on IN pipe

This patch prevents the HDM USB from submitting an URB with a buffer size
unaligned to 512 bytes to the USB subsystem.
Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/hdm-usb/hdm_usb.c

@@ -711,7 +711,7 @@ static int hdm_enqueue(struct most_interface *iface, int channel, struct mbo *mb
 				  usb_rcvbulkpipe(mdev->usb_device,
 						  mdev->ep_address[channel]),
 				  virt_address,
-				  length,
+				  length + conf->extra_len,
 				  hdm_read_completion,
 				  mbo);
 	}
@@ -771,6 +771,7 @@ static int hdm_configure_channel(struct most_interface *iface, int channel,
 	    !((conf->data_type == MOST_CH_ISOC_AVP) &&
 	      (conf->packets_per_xact != 0xFF))) {
 		mdev->padding_active[channel] = false;
+		conf->extra_len = 0;
 		goto exit;
 	}