greybus: connection: intf_cport_id is local to an interface

intf_cport_id is local to an interface and same intf_cport_id can be
used for two separate interface blocks. For finding a connection for an
interface, we are matching intf_cport_id of the connection with
cport_id, passed as argument. This is wrong, as it can match for a
connection on a different interface block.

Fix it by also comparing interface block for which connection is
requested.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>