msm8974-regulator.dtsi: adjust GFX regulator parameters

settings based on qcom documentation

Signed-off-by: Paul Reioux <reioux@gmail.com>
msm8974-regulator.dtsi: further reduce CPU retention voltage

this should help idel drain during processor retention c-state

Signed-off-by: Paul Reioux <reioux@gmail.com>