clk: keystone: sci-clk: add support for dynamically probing clocks

Currently, the driver contains a large hints table for clocks that exist
on a device, however, it is possible to probe the clocks from the firmware
also. Add support for this, and drop the clock hints table support from
the driver completely. This causes the driver to send a few extra sci-clk
messages during boot, basically one extra for each device that exists on
the SoC; on K2G this is approx 80.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>