Currently we are not initializing the scmi clock with discrete rates
correctly. We fetch the min_rate and max_rate value only for clocks with
ranges and ignore the ones with discrete rates. This will lead to wrong
initialization of rate range when clock supports discrete rate.

Fix this by using the first and the last rate in the sorted list of the
discrete clock rates while registering the clock.

Link: https://lore.kernel.org/r/20200709081705.46084-2-sudeep.holla@arm.com
Fixes: 6d6a1d82 ("clk: add support for clocks provided by SCMI")
Reviewed-by: NStephen Boyd <sboyd@kernel.org>
Reported-and-tested-by: NDien Pham <dien.pham.ry@renesas.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>