MAINTAINERS: Add git tree for Thunderbolt development

I will be gathering Thunderbolt related patches to this git tree with
help of other Thunderbolt maintainers.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -13290,6 +13290,7 @@ M:	Andreas Noever <andreas.noever@gmail.com>
 M:	Michael Jamet <michael.jamet@intel.com>
 M:	Mika Westerberg <mika.westerberg@linux.intel.com>
 M:	Yehezkel Bernat <yehezkel.bernat@intel.com>
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/westeri/thunderbolt.git
 S:	Maintained
 F:	drivers/thunderbolt/