extcon: int3496: Make the driver a bit less verbose

On all devices which I have with an INT3496 ACPI device,
there is only an ID pin defined.

Change the log-messages about not being able to get GPIOs for
"VBUS EN" and "USB MUX" to use dev_dbg().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>