gpio: MAINTAINERS: Add an entry for GPIO mockup driver

Add an entry for the GPIO mockup driver with myself as maintainer.
Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -5242,6 +5242,13 @@ L:	linux-input@vger.kernel.org
 S:	Maintained
 F:	drivers/input/touchscreen/goodix.c
 
+GPIO MOCKUP DRIVER
+M:	Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
+L:	linux-gpio@vger.kernel.org
+S:	Maintained
+F:	drivers/gpio/gpio-mockup.c
+F:	tools/testing/selftests/gpio/
+
 GPIO SUBSYSTEM
 M:	Linus Walleij <linus.walleij@linaro.org>
 M:	Alexandre Courbot <gnurou@gmail.com>