usb: dwc3: core: Fix tx/rx threshold settings

usb: dwc3: core: Fix tx/rx threshold settings

The current driver logic checks against 0 to determine whether the
periodic tx/rx threshold settings are set, but we may get bogus values
from uninitialized variables if no device property is set. Properly
default these variables to 0.

Fixes: 938a5ad1d305 ("usb: dwc3: Check for ESS TX/RX threshold config")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/cccfce990b11b730b0dae42f9d217dc6fb988c90.1649727139.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>