Drop CONFIG_DM644X_GPIO

Drop this unused option.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 5760364..07fca7b 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -38,7 +38,6 @@
 obj-$(CONFIG_TEGRA_GPIO)	+= tegra_gpio.o
 obj-$(CONFIG_TEGRA186_GPIO)	+= tegra186_gpio.o
 obj-$(CONFIG_DA8XX_GPIO)	+= da8xx_gpio.o
-obj-$(CONFIG_DM644X_GPIO)	+= da8xx_gpio.o
 obj-$(CONFIG_ALTERA_PIO)	+= altera_pio.o
 obj-$(CONFIG_MPC83XX_GPIO)	+= mpc83xx_gpio.o
 obj-$(CONFIG_MPC8XXX_GPIO)	+= mpc8xxx_gpio.o