ARM: dts: keystone: k2g: Rename the TI-SCI clocks node name

We currently use clocks as the node name for the node representing
TI-SCI clock nodes. This is better renamed to being clock-controller
as that is a better representative of the system controller function
as a clock controller for the SoC.

Reviewed-by: Tero Kristo <kristo@kernel.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>