sun6i: clock_set_pll5: Calculate k and m rather then hardcoding them

sun6i: clock_set_pll5: Calculate k and m rather then hardcoding them

Our old hardcoded k and m values are based on PLL5 being configured in steps
of 48 MHz, which is correct for sun6i where the DRAM PLL runs at twice the
DRAM CLK, which is usually configured in 24 MHz step. But on the A23 (sun8i)
the PLL5 runs at half the DRAM CLK, so we require 12 MHz steps.

This commit adjusts clock_set_pll5 to automatically select the best k and m
depending on the requested clk rate.

Suggested-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>