arm64: dts: qcom: c630: Add backlight controller

The Lenovo Yoga C630 uses the PWM controller in the TI SN65DSI86 bridge
chip to provide a signal for the backlight control and has TLMM GPIO 11
attached to some regulator that drives the backlight.

Unfortunately the regulator attached to this gpio is also powering the
camera, so turning off backlight result in the detachment of the camera
as well.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Link: https://lore.kernel.org/r/20220208041606.144039-1-bjorn.andersson@linaro.org