arm64: dts: imx8mq-pico-pi: Fix PMIC properties

Pass the required '#clock-cells' property and remove the invalid
'interrupt-names' property to fix the following schema warnings:

imx8mq-pico-pi.dtb: pmic@4b: '#clock-cells' is a required property
	from schema $id: http://devicetree.org/schemas/mfd/rohm,bd71837-pmic.yaml#
imx8mq-pico-pi.dtb: pmic@4b: 'interrupt-names' does not match any of the regexes: 'pinctrl-[0-9]+'
	from schema $id: http://devicetree.org/schemas/mfd/rohm,bd71837-pmic.yaml#



Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>