clk: rs9: Support device specific dif bit calculation

clk: rs9: Support device specific dif bit calculation

The calculation DIFx is BIT(n) +1 is only true for 9FGV0241. With
additional devices this is getting more complicated.
Support a base bit for the DIF calculation, currently only devices
with consecutive bits are supported, e.g. the 6-channel device needs
additional logic.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20230310075535.3476580-3-alexander.stein@ew.tq-group.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>