MAINTAINERS: update Muchun Song's email

I'm moving to the @linux.dev account.  Map my old addresses and update it
to my new address.

Link: https://lkml.kernel.org/r/20221208115548.85244-1-songmuchun@bytedance.com


Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>