extcon: Make static analyzer happy about union assignment

When assign unions we need to supply non-scalar value, otherwise
static analyzer is not happy:

CHECK   drivers/extcon/extcon.c
drivers/extcon/extcon.c:631:22: warning: cast to non-scalar

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