clk: thead: th1520-ap: Support setting PLL rates

clk: thead: th1520-ap: Support setting PLL rates

TH1520 ships several PLLs that could operate in either integer or
fractional mode. However, the TRM only lists a few configuration whose
stability is considered guaranteed.

Add a table-lookup rate determination logic to support PLL rate setting,
and fill up frequency-configuration tables for AP-subsystem PLLs.

Reviewed-by: Drew Fustini <fustini@kernel.org>
Signed-off-by: Yao Zi <ziyao@disroot.org>
Signed-off-by: Drew Fustini <fustini@kernel.org>