MAINTAINERS: update Vincent Mailhol's email address

Now that I have received my kernel.org account, I am changing my email
address from mailhol.vincent@wanadoo.fr to mailhol@kernel.org. The
wanadoo.fr address was my first email which I created when I was a kid
and has a special meaning to me, but it is restricted to a maximum of
50 messages per hour which starts to be problematic on threads where
many people are CC-ed.

Update all the MAINTAINERS entries accordingly and map the old address
to the new one.

I remain reachable from my old address. The different copyright
notices mentioning my old address are kept as-is for the moment. I
will update those one at a time only if I need to touch those files.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250826105255.35501-2-mailhol@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>