Blackfin: gpio: add a debounce stub

The GPIO API was extended recently to include debounce functions, but
since the on-chip Blackfin GPIO modules don't support this stuff, make
a stub in the non-GPIOLIB case so drivers build properly.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/gpio.h

@@ -279,6 +279,11 @@ static inline int gpio_direction_output(unsigned gpio, int value)
 	return bfin_gpio_direction_output(gpio, value);
 }
 
+static inline int gpio_set_debounce(unsigned gpio, unsigned debounce)
+{
+	return -EINVAL;
+}
+
 static inline int gpio_get_value(unsigned gpio)
 {
 	return bfin_gpio_get_value(gpio);