.mailmap: add Alexandre Ghiti personal email address

I'm no longer employed by Canonical which results in email bouncing so add
an entry to my personal email address.

Link: https://lkml.kernel.org/r/20230301090132.280475-1-alexghiti@rivosinc.com
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>