clk: scmi: migrate round_rate() to determine_rate()

This driver implements both the determine_rate() and round_rate() clk
ops, and the round_rate() clk ops is deprecated. When both are defined,
clk_core_determine_round_nolock() from the clk core will only use the
determine_rate() clk ops.

The existing scmi_clk_determine_rate() is a noop implementation that
lets the firmware round the rate as appropriate. Drop the existing
determine_rate implementation and convert the existing round_rate()
implementation over to determine_rate().

scmi_clk_determine_rate() was added recently when the clock parent
support was added, so it's not expected that this change will regress
anything.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Tested-by: Peng Fan <peng.fan@nxp.com> #i.MX95-19x19-EVK
Signed-off-by: Brian Masney <bmasney@redhat.com>