hw/intc/omap_intc: Remove now-unnecessary abstract base class

hw/intc/omap_intc: Remove now-unnecessary abstract base class

The OMAP interrupt controller code used to have an omap-intc
class and an omap2-intc class, which shared common code via
the abstract class common-omap-intc. Now we have deleted
omap2-intc, we don't need the separate abstract base class;
fold int into omap-intc.

Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20241003135323.1653230-1-peter.maydell@linaro.org