dt-bindings: clock: Add bindings for DA8XX CFGCHIP clocks

This adds a new binding for the clocks present in the CFGCHIP syscon
registers in TI DA8XX SoCs.

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>