phy: omap-usb2: Provide workaround for USB2PHY false disconnect

Enable the dra7x errata workaround for false disconnect problem
with USB2PHY. False disconnects were detected with some of the devices.
Reduce the sensitivity of the disconnect logic within the USB2PHY subsystem
to enusre these false disconnects are not registered.

[george.cherian@ti.com]
While at that, pass proper flags for each SoC's. This is a common driver
used across OMAP4,OMAP5,DRA7xx and AM437x USB2PHY.

False disconnect workaround is currently applicable for only DRA7x.

Signed-off-by: Austin Beam <austinbeam@ti.com>
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>