dm: gpio: add BCM6345 gpio driver

This driver is based on linux/arch/mips/bcm63xx/gpio.c, simplified to allow
defining one or two independent banks for each Broadcom SoC.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 9951611..325d053 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -21,6 +21,12 @@
 	  Select this to enable PIO for Altera devices. Please find
 	  details on the "Embedded Peripherals IP User Guide" of Altera.
 
+config BCM6345_GPIO
+	bool "BCM6345 GPIO driver"
+	depends on DM_GPIO && ARCH_BMIPS
+	help
+	  This driver supports the GPIO banks on BCM6345 SoCs.
+
 config DWAPB_GPIO
 	bool "DWAPB GPIO driver"
 	depends on DM && DM_GPIO