greybus: kill struct gmod_cport

A UniPro (short header) segment has a 5-bit field to represent a
CPort Id.  In addition, the 7-bit L3 short header holds a UniPro
device id.  There can be no more than 128 devices in a UniPro
network, but these two fields can be combined in ways to allow for
over 2000 CPorts within a single device.  As a result, a device id
is represented with one byte, and a CPort Id within a device is
always representable with a two byte value.

This patch changes integral values that reresent CPort Ids so they
use type u16 consistently.

Separately, the contents of the gmod_cport structure were mostly
fabricated, with the cport_id field being the only one that's
meaningful.  This patch gets rid of that structure, putting a
simple u16 to represent the CPort Id everywhere it had been used
before.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
es1: no BUG_ON() code, report an error and recover.