gpio: remove legacy GPIO line value setter callbacks

With no more users of the legacy GPIO line value setters - .set() and
.set_multiple() - we can now remove them from the kernel.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpiolib.c

···
 	int base = 0;
 	int ret;
 
-	/* Only allow one set() and one set_multiple(). */
-	if ((gc->set && gc->set_rv) ||
-	    (gc->set_multiple && gc->set_multiple_rv))
-		return -EINVAL;
-
 	/*
 	 * First: allocate and populate the internal stat container, and
 	 * set up the struct device.
···
 
 	lockdep_assert_held(&gc->gpiodev->srcu);
 
-	if (WARN_ON(unlikely(!gc->set && !gc->set_rv)))
+	if (WARN_ON(unlikely(!gc->set_rv)))
 		return -EOPNOTSUPP;
 
-	if (gc->set_rv) {
-		ret = gc->set_rv(gc, offset, value);
-		if (ret > 0)
-			ret = -EBADE;
+	ret = gc->set_rv(gc, offset, value);
+	if (ret > 0)
+		ret = -EBADE;
 
-		return ret;
-	}
-
-	gc->set(gc, offset, value);
-	return 0;
+	return ret;
 }
 
 static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
···
 	 * output-only, but if there is then not even a .set() operation it
 	 * is pretty tricky to drive the output line.
 	 */
-	if (!guard.gc->set && !guard.gc->set_rv && !guard.gc->direction_output) {
+	if (!guard.gc->set_rv && !guard.gc->direction_output) {
 		gpiod_warn(desc,
 			   "%s: missing set() and direction_output() operations\n",
 			   __func__);
···
 			ret = -EBADE;
 
 		return ret;
-	}
-
-	if (gc->set_multiple) {
-		gc->set_multiple(gc, mask, bits);
-		return 0;
 	}
 
 	/* set outputs if the corresponding mask bit is set */

include/linux/gpio/driver.h

···
  * @get: returns value for signal "offset", 0=low, 1=high, or negative error
  * @get_multiple: reads values for multiple signals defined by "mask" and
  *	stores them in "bits", returns 0 on success or negative error
- * @set: **DEPRECATED** - please use set_rv() instead
- * @set_multiple: **DEPRECATED** - please use set_multiple_rv() instead
  * @set_rv: assigns output value for signal "offset", returns 0 on success or
  *          negative error value
  * @set_multiple_rv: assigns output values for multiple signals defined by
···
 	int			(*get)(struct gpio_chip *gc,
 						unsigned int offset);
 	int			(*get_multiple)(struct gpio_chip *gc,
-						unsigned long *mask,
-						unsigned long *bits);
-	void			(*set)(struct gpio_chip *gc,
-						unsigned int offset, int value);
-	void			(*set_multiple)(struct gpio_chip *gc,
 						unsigned long *mask,
 						unsigned long *bits);
 	int			(*set_rv)(struct gpio_chip *gc,