mailmap: add Antoine Tenart's email

I used "Antoine Ténart" at first but then moved to a name without accent
as this cause some issues from time to time...  Add my email in the
mailmap file to have a consistent shortlog output.

Link: http://lkml.kernel.org/r/20160609130323.27706-1-antoine.tenart@free-electrons.com
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Cc: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>