arm64: dts: mt6359: Rename RTC node to match binding expectations

arm64: dts: mt6359: Rename RTC node to match binding expectations

Rename the node 'mt6359rtc' to 'rtc', as required by the binding.

Fix the following dtb-check error:

mediatek/mt8395-radxa-nio-12l.dtb: pmic: 'mt6359rtc' do not match
any of the regexes: 'pinctrl-[0-9]+'

Fixes: 3b7d143be4b7 ("arm64: dts: mt6359: add PMIC MT6359 related nodes")
Signed-off-by: Julien Massot <julien.massot@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20250514-mt8395-dtb-errors-v2-3-d67b9077c59a@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>