clk: keystone: sci-clk: cut down the clock name length

There is no need to store the full node name to the individual clocks,
as this will just consome memory and make the clock debug entries
unnecessary long. Just shorten this to "clk" for now.

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