clk: qcom: clk-rcg2: Add support for duty-cycle for RCG

The root clock generators with MND divider has the capability to support
change in duty-cycle by updating the 'D'. Add the clock ops which would
check all the boundary conditions and enable setting the desired duty-cycle
as per the consumer.

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Link: https://lore.kernel.org/r/1619334502-9880-2-git-send-email-tdas@codeaurora.org
[sboyd@kernel.org: Remove _val everywhere]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>