extcon: axp288: Remove unused platform data

This is not used / set anywhere in the tree.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>