USB: phy-msm-usb: Disable charger detection block on DISCONNECT

VBUS LOW (or DISCONNECT) may happen any time during charger detection
phase. If it happens before charger detection is complete then there
is a possibility of leaving IDP_SRC or VDP_SRC enabled which can
affect charger detection on next cable connect.

Change-Id: I266e9dced083b8cb30a960529da54c529b922faa
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>