arm64: dts: imx8mn-evk: 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: 4153f781 ("arm64: dts: imx8mn: correct interrupt flags")
Fixes: 6386156e

 ("arm64: dts: imx8mn-evk: add pca9450 for i.mx8mn-evk board")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Robin Gong <yibin.gong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>