As the .round_rate() callback returns a long clock rate, it cannot
return clock rates that do not fit in signed long, but do fit in
unsigned long.  Hence switch the divider clocks on RZ/N1 from the old
.round_rate() callback to the newer .determine_rate() callback, which
does not suffer from this limitation.

Note that range checking is not yet implemented.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/7a384d02b85cdaac4a0e2b357582c8244b9a6f98.1617282116.git.geert+renesas@glider.be