arm64: dts: mediatek: mt6795: Replace UART dummy clocks with pericfg

arm64: dts: mediatek: mt6795: Replace UART dummy clocks with pericfg

The UART nodes had a dummy clock for early bringup, as it is
expected that these are left on by the bootloader: now that
the pericfg clock controller is supported, we can replace
them with the real clocks.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221027095504.37432-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>