mailmap: Update Oliver's email address

While I'm still at Google, I've since switched to a linux.dev account
for working upstream.

Add an alias to the new address.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <20220819190158.234290-1-oliver.upton@linux.dev>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

.mailmap

@@ -330,6 +330,7 @@ Oleksij Rempel <linux@rempel-privat.de> <external.Oleksij.Rempel@de.bosch.com>
 Oleksij Rempel <linux@rempel-privat.de> <fixed-term.Oleksij.Rempel@de.bosch.com>
 Oleksij Rempel <linux@rempel-privat.de> <o.rempel@pengutronix.de>
 Oleksij Rempel <linux@rempel-privat.de> <ore@pengutronix.de>
+Oliver Upton <oliver.upton@linux.dev> <oupton@google.com>
 Pali Rohár <pali@kernel.org> <pali.rohar@gmail.com>
 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
 Patrick Mochel <mochel@digitalimplant.org>