ARM: dts: Enable the PMIC MPP ADC support for Camera ID

QRD SKUF board will use MPP4 as camera2_id and MPP6 as the
camera_id pin. The LED feature should be disabled and the
ADC function will be enabled in the SKUF devicetree.

Change-Id: I1a8b46fec69ff29d723f54e69764566701337422
Signed-off-by: Jie Cheng <rockiec@codeaurora.org>