UPSTREAM: ARM: dts: rockchip: move rk3288 io-domain nodes to the grf

UPSTREAM: ARM: dts: rockchip: move rk3288 io-domain nodes to the grf

io-voltage control is actually part of the grf, so move the node under the
newly available grf simple-mfd.

To minimize duplicate code, the core node and compatible property
gets placed in the core rk3288.dtsi while the individual boards
now only need to enable it and add the necessary supply properties.
cherry picked from commit 4b91545072ad7ca1963d2a89c8b42fc2eb561484)

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Conflicts:
	arch/arm/boot/dts/rk3288-miqi.dts
	arch/arm/boot/dts/rk3288-rock2-som.dtsi

Change-Id: I4f5ecc16524c52e8ac6f04cf8b9cdc0e1b7d937f
 (cherry picked from commit 3445b2fae55f1a232e6e4843f4f74de074d8c07f)
Signed-off-by: Jacob Chen <jacob2.chen@rock-chips.com>