usb: otg: TWL6030 Save the last event in otg_transceiver

Save the last event in the otg_transceiver so that it can used in the
musb driver and gadget driver to configure the musb and enable the
vbus for host mode and OTG mode, if the device is connected during boot.

Signed-off-by: Hema HK <hemahk@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>