gpio: Rename free() to rfree()

This function name conflicts with our desire to #define free() to
something else on sandbox. Since it deals with resources, rename it to
rfree().

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index d6cf187..05777e6 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -248,7 +248,7 @@
  */
 struct dm_gpio_ops {
 	int (*request)(struct udevice *dev, unsigned offset, const char *label);
-	int (*free)(struct udevice *dev, unsigned offset);
+	int (*rfree)(struct udevice *dev, unsigned int offset);
 	int (*direction_input)(struct udevice *dev, unsigned offset);
 	int (*direction_output)(struct udevice *dev, unsigned offset,
 				int value);