Parking bits might not be cleared by the bootloader properly (if for
instance it doesn't use the device configured by that pin). Clear
the park bits for all the pins during pinctrl probe.

This is present on T210 platforms but not earlier ones, so for earlier
generations, set parked_reg = -1 to disable.

The park bit is used to prevent glitching when reprogramming pinctrl
registers.

Based on work by:
Shravani Dingari <shravanid@nvidia.com>
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>