usb: phy: fsm: update OTG HNP state transition conditions according to OTG and EH 2.0 spec.

According to:"On-The-Go and Embedded Host Supplement to the USB Revision 2.0
Specification July 27, 2012 Revision 2.0 version 1.1a"
- From a_host to a_wait_bcon if !b_conn
- Add transition from a_host to a_wait_vfall if id state is high or a_bus_drop
- From a_wait_vfall to a_idle if a_wait_vfall_tmout

Signed-off-by: Li Jun <b47624@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>