rockchip: clk: rk3368: implement bandwidth adjust for PLLs

The RK3368 TRM recommends to configure the bandwith adjustment (CON2)
for PLLs to NF/2.  This implements this for all reconfigurations of
PLLs and removes the 'has_bwadj' flag (as the RK3368 always has the
bandwidth-adjustment feature according to its manual).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>