gpio / ACPI: Avoid unnecessary checks in __gpiod_get_index()

If dev is NULL in __gpiod_get_index() and both ACPI and OF are
enabled, it will be checked twice before the code decides to give
up with DT/ACPI lookup, so avoid that.

Also use the observation that ACPI_COMPANION() is much more efficient
than ACPI_HANDLE(), because the latter uses the former and carries out
a check and a pointer dereference on top of it, so replace the
ACPI_HANDLE() check with an ACPI_COMPANION() one which does not
require the additional IS_ENABLED(CONFIG_ACPI) check too.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Acked-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -1971,13 +1971,15 @@ struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
 
 	dev_dbg(dev, "GPIO lookup for consumer %s\n", con_id);
 
-	/* Using device tree? */
-	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node) {
-		dev_dbg(dev, "using device tree for GPIO lookup\n");
-		desc = of_find_gpio(dev, con_id, idx, &lookupflags);
-	} else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev)) {
-		dev_dbg(dev, "using ACPI for GPIO lookup\n");
-		desc = acpi_find_gpio(dev, con_id, idx, &lookupflags);
+	if (dev) {
+		/* Using device tree? */
+		if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
+			dev_dbg(dev, "using device tree for GPIO lookup\n");
+			desc = of_find_gpio(dev, con_id, idx, &lookupflags);
+		} else if (ACPI_COMPANION(dev)) {
+			dev_dbg(dev, "using ACPI for GPIO lookup\n");
+			desc = acpi_find_gpio(dev, con_id, idx, &lookupflags);
+		}
 	}
 
 	/*