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>

MAINTAINERS

@@ -7153,6 +7153,7 @@ F:	drivers/crypto/picoxcell*
 
 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/