extcon: Add the EXTCON_CHG_USB_SDP to support SDP charing port

This patch adds the new EXTCON_CHG_USB_SDP connector to support SDP (Standard
Downstream Port) USB charging port. The commit 11eecf91 ("extcon: Modify
the id and name of external connector") add the new EXTCON_CHG_USB_SDP
connector which support the both data transfer and usb charging at the same
time.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>