extcon: Remove dup device name in the message and unneeded error check

The device name is already printed with dev_err(), no need to repeat.
The device pointer itself is not supposed to be an error point, drop
that check.

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