greybus: es2: disable cport-in after remove greybus host device

This allows greybus to do operations before being removed.

Tested by removing the gb-es2.ko module on both EVT1.5 and qemu with
gbsim. The driver removes the greybus host device successfully before
disabling the urbs. The errors are still coming ("urb cport in error -2
(dropped)"), but with an error value -2 (ENOENT) instead of -108. And
that happens while the urbs are disabled, not while doing greybus
operations.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: David Lin <dtwlin@google.com>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>