arm64: dts: mediatek: mt6797: Fix 26M oscillator unit name

[ Upstream commit 5f535cc583759c9c60d4cc9b8d221762e2d75387 ]

Update its unit name to oscillator-26m and remove the unneeded unit
address to fix a unit_address_vs_reg warning.

Fixes: 464c510f ("arm64: dts: mediatek: add mt6797 support")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221013152212.416661-9-angelogioacchino.delregno@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>