pinctrl: use linux-gpio mailing list

The GPIO concepts are close enough to pin control that we may use
the same mailing list to discuss them.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index a20df9b..d7df791 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7153,6 +7153,7 @@
 
 PIN CONTROL SUBSYSTEM
 M:	Linus Walleij <linus.walleij@linaro.org>
+L:	linux-gpio@vger.kernel.org
 S:	Maintained
 F:	drivers/pinctrl/
 F:	include/linux/pinctrl/