UFS card support is removed from Kona, thus storage card detect GPIO
based extcon support added for UFS card is no longer used. This change
reverts commit ea32f8eecb ("dt-bindings: extcon: storage-cd-gpio: add
storage card detect GPIO extcon").
Change-Id: Ia9f1a66685a5bae6cc79e248191c4546fa9b3cdc