USB: msm_otg: Add support for Userspace charger detection

The userspace charger detection takes place when a standard dedicated
charger is connected.  We handover the detection part to userspace
after detecting the dedicated charger.  Create a character device
called /dev/usb_ext_chg to expose hardware register access and a
mechanism to vote against low power mode.  Add POWER_SUPPLY_PROP_TYPE
property to power_supply_property array to send charger type information
in power supply uevent.

CRs-Fixed: 500279
Change-Id: I538601a423e5bc87e98d29690c0da50b96f8e481
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>