greybus: create host device cport id map

greybus: create host device cport id map

A Greybus host device has a pool of CPort Ids it can use.  When we
establish a connection with a CPort on another module we will need
to allocate one from those that are available.

This patch adds a bitmap to the greybus host device structure that
allows cport ids to be allocated and freed as needed.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>