gpio: crystalcove: Use -ENOTSUPP consistently

[ Upstream commit ace0ebe5c98d66889f19e0f30e2518d0c58d0e04 ]

The GPIO library expects the drivers to return -ENOTSUPP in some
cases and not using analogue POSIX code. Make the driver to follow
this.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>