This pll code is primarily based on the code from the kendryte standalone
sdk in lib/drivers/sysctl.c. k210_pll_calc_config is roughly analogous to
the algorithm used to set the pll frequency, but it has been completely
rewritten to be fixed-point based.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
CC: Lukasz Majewski <lukma@denx.de>
