clk: sunxi-ng: a64: allow pll-mipi to set parent's rate

The nkm clock now supports setting the parent's rate. Utilize this
option to find the optimal rate for pll-mipi.

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
Link: https://lore.kernel.org/r/20230807-pll-mipi_set_rate_parent-v6-3-f173239a4b59@oltmanns.dev
Signed-off-by: Chen-Yu Tsai <wens@csie.org>