mailmap: Update email for Asahi Lina

Add an alias so I can more easily filter kernel-related emails.

Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Link: https://lore.kernel.org/r/20250409-mailmap-lina-email-v1-1-265d05848ae3@asahilina.net


Signed-off-by: Sven Peter <sven@svenpeter.dev>