mfd: sun6i-prcm: Fix build warning for non-OF configurations

When CONFIG_OF is disabled, we get a harmless warning about an
unused variable:

drivers/mfd/sun6i-prcm.c: In function 'sun6i_prcm_probe':
drivers/mfd/sun6i-prcm.c:151:22: error: unused variable 'np' [-Werror=unused-variable]

Remove the variable and open-code the value in the only place
it is used, so it can get left out as well without CONFIG_OF.

Fixes: a05a2e79 ("mfd: sun6i-prcm: Allow to compile with COMPILE_TEST")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/sun6i-prcm.c

@@ -148,13 +148,12 @@ static const struct of_device_id sun6i_prcm_dt_ids[] = {
 
 static int sun6i_prcm_probe(struct platform_device *pdev)
 {
-	struct device_node *np = pdev->dev.of_node;
 	const struct of_device_id *match;
 	const struct prcm_data *data;
 	struct resource *res;
 	int ret;
 
-	match = of_match_node(sun6i_prcm_dt_ids, np);
+	match = of_match_node(sun6i_prcm_dt_ids, pdev->dev.of_node);
 	if (!match)
 		return -EINVAL;