extcon: storage-cd-gpio: Remove storage card detect gpio based extcon

UFS card support is removed from Kona, thus the storage card detect gpio
based extcon support added for UFS card is no longer needed. This change
reverts commit 9a6d9821 ("extcon: storage-cd-gpio: add storage card
detect gpio based extcon").

Change-Id: If91eb36ebaffdc9d9b643ed54733506ab7b357e9
Signed-off-by: Can Guo <cang@codeaurora.org>