usb: msm_otg: Allow delayed LPM upon cable disconnect

This change introduces a new module parameter,
which allows to use 1 second delay before entering Low
Power Mode, after USB cable is disconnected.

This change is needed, since for some platforms, there
are external HW blocks (e.g., A2) that interact with USB
shortly after USB cable is disconnected, and require USB
clocks to be enabled.

Change-Id: Ia63839e84ec1c7ab8816ad1b035f1026acaa1e66
Signed-off-by: Amit Blay <ablay@codeaurora.org>