clk: sprd: Composite driver support offset config

The composite interface support the offset configuration,
which is used to support mux and div in different registers.
Because some sprd projects, the divider has different
addresses from mux for one composite clk.

Signed-off-by: Zhifeng Tang <zhifeng.tang@unisoc.com>
Reviewed-by: Chunyan Zhang <zhang.lyra@gmail.com>
Link: https://lore.kernel.org/r/20230913115211.11512-1-zhifeng.tang@unisoc.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>