MAINTAINERS: Add gpio regmap section

Add myself as a reviewer for the gpio regmap.
Signed-off-by: NMichael Walle <michael@walle.cc>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200528145845.31436-4-michael@walle.ccSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -7249,6 +7249,12 @@ S:	Maintained
 F:	drivers/gpio/gpio-mockup.c
 F:	tools/testing/selftests/gpio/
 
+GPIO REGMAP
+R:	Michael Walle <michael@walle.cc>
+S:	Maintained
+F:	drivers/gpio/gpio-regmap.c
+F:	include/linux/gpio/regmap.h
+
 GPIO SUBSYSTEM
 M:	Linus Walleij <linus.walleij@linaro.org>
 M:	Bartosz Golaszewski <bgolaszewski@baylibre.com>