ARM: dts: Add generic ti,sysc compatible in addition to the custom ones

Otherwise we cannot use generic OF_DEV_AUXDATA match without listing
all the compatibles separately for OF_DEV_AUXDATA. Let's also update the
binding accordingly.

Let's also fix omap4.dtsi to use "ti,sysc-omap4-sr" compatible as we
have documented in the binding. This was not noticed earlier as we're
still probing SmartReflex driver with platform data.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>