MAINTAINERS: update Broadcom Cygnus SoC git tree

The Cygnus SoC git tree is moved from github.com/brcm/linux.git to its
own git tree at github.com/broadcom/cygnus-linux.git.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

MAINTAINERS

@@ -2192,7 +2192,7 @@ M:	Ray Jui <rjui@broadcom.com>
 M:	Scott Branden <sbranden@broadcom.com>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 L:	bcm-kernel-feedback-list@broadcom.com
-T:	git git://git.github.com/brcm/linux.git
+T:	git git://git.github.com/broadcom/cygnus-linux.git
 S:	Maintained
 N:	iproc
 N:	cygnus