.mailmap: Add an entry for my work email address

Collect a few very old previous employers as well.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

.mailmap

@@ -153,6 +153,9 @@ Christian Brauner <brauner@kernel.org> <christian.brauner@ubuntu.com>
 Christian Marangi <ansuelsmth@gmail.com>
 Christophe Ricard <christophe.ricard@gmail.com>
 Christoph Hellwig <hch@lst.de>
+Chuck Lever <chuck.lever@oracle.com> <cel@kernel.org>
+Chuck Lever <chuck.lever@oracle.com> <cel@netapp.com>
+Chuck Lever <chuck.lever@oracle.com> <cel@citi.umich.edu>
 Claudiu Beznea <claudiu.beznea@tuxon.dev> <claudiu.beznea@microchip.com>
 Colin Ian King <colin.i.king@gmail.com> <colin.king@canonical.com>
 Corey Minyard <minyard@acm.org>