usb: phy: tahvo: fix smatch warnings

phy-tahvo introduced the following smatch warnings:

drivers/usb/phy/phy-tahvo.c:203 tahvo_usb_set_host() warn: variable dereferenced before check 'otg' (see line 199)
drivers/usb/phy/phy-tahvo.c:235 tahvo_usb_set_peripheral() warn: variable dereferenced before check 'otg' (see line 231)

Fix by deleting bogus NULL pointer checks. The USB framework will always
call us with a valid OTG pointer.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/phy/phy-tahvo.c

@@ -200,9 +200,6 @@ static int tahvo_usb_set_host(struct usb_otg *otg, struct usb_bus *host)
 
 	dev_dbg(&tu->pt_dev->dev, "%s %p\n", __func__, host);
 
-	if (otg == NULL)
-		return -ENODEV;
-
 	mutex_lock(&tu->serialize);
 
 	if (host == NULL) {
@@ -232,9 +229,6 @@ static int tahvo_usb_set_peripheral(struct usb_otg *otg,
 
 	dev_dbg(&tu->pt_dev->dev, "%s %p\n", __func__, gadget);
 
-	if (!otg)
-		return -ENODEV;
-
 	mutex_lock(&tu->serialize);
 
 	if (!gadget) {