doc: replace @return by Return:

Sphinx expects Return: and not @return to indicate a return value.

find . -name '*.c' -exec \
sed -i 's/^\(\s\)\*\(\s*\)@return\(\s\)/\1*\2Return:\3/' {} \;

find . -name '*.h' -exec \
sed -i 's/^\(\s\)\*\(\s*\)@return\(\s\)/\1*\2Return:\3/' {} \;

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

include/button.h

@@ -46,7 +46,7 @@ struct button_ops {
  *
  * @label:	button label to look up
  * @devp:	Returns the associated device, if found
- * @return 0 if found, -ENODEV if not found, other -ve on error
+ * Return: 0 if found, -ENODEV if not found, other -ve on error
  */
 int button_get_by_label(const char *label, struct udevice **devp);
 
@@ -54,7 +54,7 @@ int button_get_by_label(const char *label, struct udevice **devp);
  * button_get_state() - get the state of a button
  *
  * @dev:	button device to change
- * @return button state button_state_t, or -ve on error
+ * Return: button state button_state_t, or -ve on error
  */
 enum button_state_t button_get_state(struct udevice *dev);