extcon: int3496: Convert to use SPDX identifier

Convert driver to use SPDX identifier.

While here, fix MODULE_LICENSE() string to be the same as license text states.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>