arm64: dts: mediatek: mt6795: Remove incorrect fixed-clocks

Remove the RTC and UART fixed clocks, as these were introduced to
temporarily provide a dummy clock to devices: since the two 26M/32K
fixed oscillators clocks (which do really exist in the SoC) have
been added, there's no reason to keep the aforementioned (and now
redundant) dummies in this devicetree.

In order to remove the uart dummy clock, it was necessary to also
reassign the clock of all UART nodes to clk26m.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220609112303.117928-7-angelogioacchino.delregno@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>