pinctrl: tegra-xusb: testing wrong variable in probe()

There is a cut and paste bug so we test the wrong variable.  "err" is
never less than zero at this point.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>