clk: scmi: Add support for get/set duty_cycle operations

Provide the CLK framework callbacks related to get/set clock duty cycle if
the related SCMI clock supports OEM extended configurations.

CC: Michael Turquette <mturquette@baylibre.com>
CC: Stephen Boyd <sboyd@kernel.org>
CC: linux-clk@vger.kernel.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240415163649.895268-6-cristian.marussi@arm.com
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>