Add trace events for GPU and CPU IRQs.

Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20201017180731.1165871-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>