nitrogen6x: configure SGTL5000, CSI camera clock outputs

Configure CLKO outputs for SGTL5000, CSI camera.

The sys_mclk output for the SGTL500 in particular prevents
Windows CE from properly driving audio.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>