MAINTAINERS: add myself as counter watch events tool maintainer

Add MAINTAINERS entry for the counter watch events tool. William has
been asking to add at least me as the point of contact for this utility.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20231213173117.4174511-3-fabrice.gasnier@foss.st.com


Signed-off-by: William Breathitt Gray <william.gray@linaro.org>