usb: ehci-msm-hsic: Disable HSIC on driver unbind

Keeping HSIC enabled in PHY register increases power
leakage as long as PHY is powered.
Disable HSIC as part of driver_remove to minimize leakage
from HSIC PHY if not in use.

Change-Id: Ic246b972424c1e1be9dc8292b804e5be0578db64
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>