usb: phy-msm: Avoid SE1 linestate after enabling DCD

During PHY based charger detection, SE1 linestate may occur
as driver enables current source first and then DP pull-down.
This may affect charger detection.Apply DM pulldown before
enabling current source on DP to  avoid SE1 state.

Change-Id: I01cb4ad4b97145c12d211c6b2c9035f6a9953d9b
Signed-off-by: Arumuga Durai A <cadurai@codeaurora.org>