mailmap: add entries for Heiko Stuebner

I am going to lose my vrull.eu address at the end of july, and while
adding it to mailmap I also realised that there are more old addresses
from me dangling, so update .mailmap for all of them.

Link: https://lkml.kernel.org/r/20230704163919.1136784-3-heiko@sntech.de


Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>