clk: scmi: Add support for .is_enabled clk_ops

clk: scmi: Add support for .is_enabled clk_ops

Add support for .is_enabled atomic clk_ops using the related SCMI clock
operation in atomic mode, if available.

Note that the .is_enabled callback will be supported by this SCMI clock
driver only if the configured underlying SCMI transport does support atomic
operations.

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>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20230826125308.462328-6-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>