arm64: dts: allwinner: a64: Run GPU at 432 MHz

arm64: dts: allwinner: a64: Run GPU at 432 MHz

The Allwinner A64's GPU has currently three operating points. However,
the BSP runs the GPU fixed at 432 MHz. In addition, at least one of the
devices using that SoC - the pinephone - shows unstabilities (see link)
that can be circumvented by running the GPU at a fixed rate.

Therefore, remove the other two operating points from the GPU OPP table,
so that the GPU runs at a fixed rate of 432 MHz.

Link: https://gitlab.com/postmarketOS/pmaports/-/issues/805
Acked-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20240310-pinephone-pll-fixes-v4-5-46fc80c83637@oltmanns.dev
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>