Trying to send an email to mtd@infradead.org gives you the answer that 
you should use linux-mtd@lists.infradead.org instead.

So let's update the entry in MAINTAINERS.
Signed-off-by: Adrian Bunk <bunk@fs.tum.de>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>