usb: dwc3: Fix dereferencing of null dwc->usb_psy

usb: dwc3: Fix dereferencing of null dwc->usb_psy

Currently the null check logic on dwc->usb_psy is inverted as it allows
calls to power_supply_put with a null dwc->usb_psy causing a null
pointer dereference. Fix this by removing the ! operator.

Addresses-Coverity: ("Dereference after null check")
Fixes: 59fa3def35de ("usb: dwc3: add a power supply for current control")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210303095826.6143-1-colin.king@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>