greybus: es2: dynamically allocate array for cport <-> ep mapping

In order to be able to dynamically determine the number of CPorts supported
by the UniPro IP instead of hardcoding the value we need to dynamically
allocate the array that is doing the cport-ep mapping.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>