ENGR00331016-5 usb: chipidea: otg: clear b_bus_req when vbus is off

ENGR00331016-5 usb: chipidea: otg: clear b_bus_req when vbus is off

In case of b_peripheral --> b_wait_acon --> b_idle due to vbus off
in b_wait_acon state, b_bus_req cannot be cleared in b_idle state,
which result in b device will do data pulse because b_bus_req is set.
This patch fix this issue by clear the input variable b_bus_req when
vbus is off.

Acked-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Li Jun <b47624@freescale.com>
(cherry picked from commit bc600546bf9193f1a39186ad4c07a5fd497c7bfd)