arm64: dts: hisilicon: remove unused property pinctrl-names

uart1 and uart5 are not used as pinctrl, so the property "pinctrl-names"
can be deleted. In fact, the property "pinctrl-names" depends on the
property "pinctrl-0". So the errors similar to the following will be
reported by pinctrl-consumer.yaml.

serial@fdf00000: 'pinctrl-0' is a dependency of 'pinctrl-names'

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>