pinctrl: MAINTAINERS: add git tree reference

Reference my pinctrl GIT tree @kernel.org

Reported-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -7400,6 +7400,7 @@ F:	drivers/crypto/picoxcell*
 PIN CONTROL SUBSYSTEM
 M:	Linus Walleij <linus.walleij@linaro.org>
 L:	linux-gpio@vger.kernel.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git
 S:	Maintained
 F:	drivers/pinctrl/
 F:	include/linux/pinctrl/