dt-bindings: omap: Add clock-output-names and #clock-cells

This allows us to use clock-output-names for the clock manager instance
name instead of relying on non-standard node names.

Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Tero Kristo <kristo@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Rob Herring <robh@kernel.org>
Message-Id: <20220203112337.19821-1-tony@atomide.com>