MAINTAINERS: Add thunderbolt.h to the Thunderbolt driver entry

The new API header (include/linux/thunderbolt.h) is maintained by the
Thunderbolt driver maintainers.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NMichael Jamet <michael.jamet@intel.com>
Reviewed-by: NYehezkel Bernat <yehezkel.bernat@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -13278,6 +13278,7 @@ M:	Mika Westerberg <mika.westerberg@linux.intel.com>
 M:	Yehezkel Bernat <yehezkel.bernat@intel.com>
 S:	Maintained
 F:	drivers/thunderbolt/
+F:	include/linux/thunderbolt.h
 
 THUNDERX GPIO DRIVER
 M:	David Daney <david.daney@cavium.com>