pinctrl: cherryview: Return correct value if pin in push-pull mode

Currently the getter returns ENOTSUPP on pin configured in
the push-pull mode. Fix this by adding the missed switch case.

Fixes: ccdf81d0 ("pinctrl: cherryview: add option to set open-drain pin config")
Fixes: 6e08d6bb ("pinctrl: Add Intel Cherryview/Braswell pin controller support")
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>