usb: dwc3-msm: Retry if vbus regulator_get fails with -EPROBE_DEFER

Device bootup with USB A-cable connected, will call start_host in
UNDEFINED state. The vbus regulator_get may fail with -EPROBE_DEFER
if the regulator driver is not ready and hence device will fail to
switch to HOST mode.
Set the state as A_IDLE which then schedules sm_work after 1sec
in case of regulator_get fails with -EPROBE_DEFER, so that it calls
start_host again.

Change-Id: Iac266c4dcea3b213682ed4f70e52691617166aeb
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>