i2c: designware: Consider SCL GPIO optional

GPIO library can return -ENOSYS for the failed request.
Instead of failing ->probe() in this case override error code to 0.

Fixes: ca382f5b

 ("i2c: designware: add i2c gpio recovery option")
Reported-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>