ARM: dts: Add clock-output-names for omap4

To stop using the non-standard node name based clock naming, let's
first add the clock-output-names property. This allows us to stop using
the internal legacy clock naming and unify the naming for the TI SoCs in
the following patches.

Note that we must wait on fixing the node naming issues until after the
internal clock names have been updated to avoid adding name translation
unnecessarily.

Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Tero Kristo <kristo@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Message-Id: <20220204084339.12341-2-tony@atomide.com>