ARMv7M: Add STM32F4 support

Signed-off-by: Kamil Lulko <rev13@wp.pl>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 85f71c5..8ca8b05 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -42,3 +42,4 @@
 oby-$(CONFIG_SX151X)		+= sx151x.o
 obj-$(CONFIG_SUNXI_GPIO)	+= sunxi_gpio.o
 obj-$(CONFIG_LPC32XX_GPIO)	+= lpc32xx_gpio.o
+obj-$(CONFIG_STM32_GPIO)	+= stm32_gpio.o