MAINTAINERS: update arch/tile maintainer email domain

Mellanox has acquired EZchip, so my email address as arch/tile
maintainer changes to cmetcalf@mellanox.com.

  http://www.mellanox.com/page/press_release_item?id=1681

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

MAINTAINERS

@@ -10940,7 +10940,7 @@ F:	include/uapi/linux/tipc*.h
 F:	net/tipc/
 
 TILE ARCHITECTURE
-M:	Chris Metcalf <cmetcalf@ezchip.com>
+M:	Chris Metcalf <cmetcalf@mellanox.com>
 W:	http://www.ezchip.com/scm/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile.git
 S:	Supported