greybus: descriptor type updates

greybus: descriptor type updates

Some more updates to the definition of a manifest descriptor.
    - We get rid of function descriptors.  The type of function is
      easily specified with the CPort it uses.
    - Add a new interface descriptor type.
    - Clean up the CPort descriptor structure, eliminating fields
      that serve no purpose and adding the function id field

The sysfs stuff will be updated a little later to add entries
for the Greybus interfaces associated with modules.

Rearrange the order of a few things in "greybus_manifest.h".

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