clk: ingenic: Make PLL clock "od" field optional

Add support for defining PLL clocks with od_bits = 0, meaning that
OD is fixed to 1 and there is no OD field in the register. In this
case od_max must also be 0, which is enforced with BUG_ON().

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/r/20221026194345.243007-2-aidanmacdonald.0x0@gmail.com


Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>