MAINTAINERS: Add Maira to V3D maintainers

I've been contributing to V3D with improvements, reviews, testing and
debugging. Therefore, add myself as a co-maintainer of the V3D driver.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Melissa Wen <mwen@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231106134201.725805-1-mcanal@igalia.com