power: supply: wm831x: Check wm831x_set_bits() return value

Since wm831x_set_bits() may return error, log failure and exit from
wm831x_usb_limit_change() in such case.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 626b6cd5f52e ("power: wm831x_power: Support USB charger current limit management")
Signed-off-by: Ivan Abramov <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/wm831x_power.c

···
 							 struct wm831x_power,
 							 usb_notify);
 	unsigned int i, best;
+	int ret;
 
 	/* Find the highest supported limit */
 	best = 0;
···
 	dev_dbg(wm831x_power->wm831x->dev,
 		"Limiting USB current to %umA", wm831x_usb_limits[best]);
 
-	wm831x_set_bits(wm831x_power->wm831x, WM831X_POWER_STATE,
-		        WM831X_USB_ILIM_MASK, best);
+	ret = wm831x_set_bits(wm831x_power->wm831x, WM831X_POWER_STATE,
+			      WM831X_USB_ILIM_MASK, best);
+	if (ret < 0) {
+		dev_err(wm831x_power->wm831x->dev,
+			"Failed to set USB current limit: %d\n", ret);
+		return ret;
+	}
 
 	return 0;
 }