MAINTAINERS: fix git tree url for musb module

Commit 3b243519 ("MAINTAINERS: drop OMAP USB and MUSB
maintainership") switched the maintainer for musb module, but didn't
update the git tree location.

Delete the git tree information, since the current maintainer doesn't
have a public tree.
Reported-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -9213,7 +9213,6 @@ F:	include/linux/isicom.h
 MUSB MULTIPOINT HIGH SPEED DUAL-ROLE CONTROLLER
 M:	Bin Liu <b-liu@ti.com>
 L:	linux-usb@vger.kernel.org
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git
 S:	Maintained
 F:	drivers/usb/musb/