arm64: dts: imx8mm-beacon-som: fix missing PMIC's interrupt line pull-up

The PMIC's interrupt is level low and should be pulled up.  The PMIC's
device node had pinctrl-0 property but it lacked pinctrl-names which
is required to apply the pin configuration.

Fixes: 5f67317b ("arm64: dts: imx8mm: correct interrupt flags")
Fixes: 593816fa ("arm64: dts: imx: Add Beacon i.MX8m-Mini development kit")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>