Input: axp20x-pek - use our own device for errors

Before this commit axp20x-pek was mixing 2 style error reporting calls:
dev_err(&pdev->dev, ...);
dev_err(axp20x->dev, ...);

But the second is our parent device, not our own device, so switch to
using &pdev->dev everywhere.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>