linux: userspace GPIO control

Allow use host GPIO pins for non-realtime purposes.

Signed-off-by: Andrey Kunitsyn <blackicebox@gmail.com>

src/linux/Kconfig

@@ -10,6 +10,8 @@ config LINUX_SELECT
     select HAVE_GPIO_SPI
     select HAVE_GPIO_HARD_PWM
     select HAVE_GPIO_I2C
+    select HAVE_GPIO_BITBANGING
+    select HAVE_GPIO
 
 config BOARD_DIRECTORY
     string