clk: qcom: clk-rcg: add clk_rcg_floor_ops ops

Add clk_rcg_floor_ops for clock that can't provide a stable freq and
require to use a floor freq to provide the requested frequency.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Tested-by: Jonathan McDowell <noodles@earth.li>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220226135235.10051-10-ansuelsmth@gmail.com