dt-bindings: clock: ti-sci: Fix incorrect usage of headers

The clock consumer usage description was erroneously referring to
couple of dt-binding headers that are no longer valid. The definition
and/or usage of these headers is incorrect and the only file present
at the moment, dt-bindings/soc/k2g.h is also being cleaned up. The
examples in this binding were updated properly, but the update to
description was missed out. So, fix this.

Fixes: 8f306cfe ("Documentation: dt: Add TI SCI clock driver")
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Rob Herring <robh@kernel.org>