phy: tegra: xusb: remove unused variable

The local variable @priv is set but not used, can be removed

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>