pinctrl: merrifield: Fix open-drain pin mode configuration

Currently the pin may not be configured as open-drain in some
cases because the argument may be 0 for the boolean types of
the pin configurations. Fix this by ignoring the argument.

With that, allow to actually restore pin to the push-pull mode.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>