phy: phy-bcm-ns2-usbdrd: Broadcom USB DRD PHY driver for Northstar2

This is driver for USB DRD PHY used in Broadcom's Northstar2
SoC. The phy can be configured to be in Device mode or Host
mode based on the type of cable connected to the port. The
driver registers to  extcon framework to get appropriate
connect events for Host/Device cables connect/disconnect
states based on VBUS and ID interrupts.

Signed-off-by: Raviteja Garimella <raviteja.garimella@broadcom.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>