drivers: usb: fsl: Workaround for Erratum A004477

Add a delay of 1 microsecond before issuing soft reset to the
controller to let ongoing ULPI transaction complete.
This prevents corruption of ULPI Function Control Register which
eventually prevents phy clock from entering to low power mode

Signed-off-by: Nikhil Badola <nikhil.badola@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>