USB-Serial: Fix error handling of usb_wwan

This fixes an issue where the bulk-in urb used for incoming data transfer
is not resubmitted if the packet recieved contains an error status.  This
results in the driver locking until the port is closed and re-opened.

Tested on a custom board with a Cinterion GSM module.

Signed-off-by: Matt Burtch <matt@grid-net.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>