mailmap: add Johan Hovold

Add two entries to map to my primary address.

Link: http://lkml.kernel.org/r/1473850348-19177-1-git-send-email-johan@kernel.org


Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>