MAINTAINERS: Add myself as mlx5 core and mlx5e co-maintainer

I have been working on mlx5 related code for several years,
contributing features, code reviews, and occasional maintainer tasks
when needed. This patch makes my maintainer role official.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://patch.msgid.link/20250627014252.1262592-1-saeed@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>