usb: musb: Add musb git tree to maintainers entry

Trivial patch adding musb's git tree to MAINTAINERS file.
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>

MAINTAINERS

@@ -2978,6 +2978,7 @@ MUSB MULTIPOINT HIGH SPEED DUAL-ROLE CONTROLLER
 P:	Felipe Balbi
 M:	felipe.balbi@nokia.com
 L:	linux-usb@vger.kernel.org
+T:	git gitorious.org:/musb/mainline.git
 S:	Maintained
 
 MYRICOM MYRI-10G 10GbE DRIVER (MYRI10GE)