hw/intc/arm_gicv3_its: Add trace events for table reads and writes

hw/intc/arm_gicv3_its: Add trace events for table reads and writes

For debugging guest use of the ITS, it can be helpful to trace
when the ITS reads and writes the in-memory tables.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220303202341.2232284-3-peter.maydell@linaro.org