arm64: dts: rockchip: drop #address-cells, #size-cells from rk3399 pmugrf node

arm64: dts: rockchip: drop #address-cells, #size-cells from rk3399 pmugrf node

The device tree compiler gives the following warning:

    /syscon@ff100000: unnecessary #address-cells/#size-cells without
    "ranges" or child "reg" property

Since the pmygrf node only has an io-domains child node that has no
reg property, remove the two properties from the pmugrf node to silence
the warning.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20200327030414.5903-6-wens@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>