USB: serial: Fix mos7840 timeout

* mos7840 driver was using multiple of HZ for the timeout handed off to
  usb_control_msg().  Changed the timeout to use msecs instead.

* Remove unused WAIT_FOR_EVER definition

Signed-off-by: Mark Ferrell <mferrell@uplogix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>