pinctrl: add driver for meson-gxbb pin controller

Add a pin controller driver for Meson GXBB adapted from Linux kernel.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/Makefile b/drivers/pinctrl/Makefile
index c92ab8c..f28b5c1 100644
--- a/drivers/pinctrl/Makefile
+++ b/drivers/pinctrl/Makefile
@@ -14,3 +14,4 @@
 obj-$(CONFIG_PINCTRL_UNIPHIER)	+= uniphier/
 obj-$(CONFIG_PIC32_PINCTRL)	+= pinctrl_pic32.o
 obj-$(CONFIG_PINCTRL_EXYNOS)	+= exynos/
+obj-$(CONFIG_PINCTRL_MESON)	+= meson/