mailmap: add entry for Christian Marangi

Add entry to map ansuelsmth@gmail.com to the unique identity of
Christian Marangi.

Link: https://lkml.kernel.org/r/20220615225012.18782-1-ansuelsmth@gmail.com
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>