mailmap: update/replace my old email addresses

I was recently reminded by someone who was unable to reach my old
email address that I really should update the kernel's .mailmap
so that people looking for me in old commits can reach my current
email.

Signed-off-by: Paul Moore <[e-mail]>

.mailmap

···
 Paul E. McKenney <[e-mail]> <[e-mail]>
 Paul Mackerras <[e-mail]> <[e-mail]>
 Paul Mackerras <[e-mail]> <[e-mail]>
+Paul Moore <[e-mail]> <[e-mail]>
+Paul Moore <[e-mail]> <[e-mail]>
 Pavankumar Kondeti <[e-mail]> <[e-mail]>
 Peter A Jonsson <[e-mail]>
 Peter Oruba <[e-mail]>