extcon: palmas: Hide error messages if gpio returns -EPROBE_DEFER

If the gpios are probed after this driver (e.g. if they
come from an i2c expander) there is no need to print an
error message.

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>