greybus: fix sparse warning in manifest.c

The cport id field is a le16, so treat it as such when comparing it to
something else.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>