PM / devfreq: imx: Register interconnect device

There is no single device which can represent the imx interconnect.
Instead of adding a virtual one just make the main &noc act as the
global interconnect provider.

The imx interconnect provider driver will scale the NOC and DDRC based
on bandwidth request. More scalable nodes can be added in the future,
for example for audio/display/vpu/gpu NICs.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>