clk: keystone: sci-clk: extend clock IDs to 32 bits

Currently, the clock identifiers are limited to 255. To support future
SoCs, this muse be extended to 32 bits, which should provide way more
than enough space. Basic support for extending the clock API is going
to be implemented in the firmware driver, but there are some minor
changes that need to be done on the clock driver side first.

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