usb: cdns3: gadget: set fast access bit

Below is the recommendation from Cadence designer:
	Using this bit to be sure that PHY clock is keeping up in active
	state. It's good to keep Fast Access bit enabled as long as there
	is any access to USB register.

It is used to fix the potential ARM core hang when visit controller
register after DEVDS (.pullup is cleared) is set, the threaded irq
may be scheduled at that time.

Cc: Pawel Laszczak <pawell@cadence.com>
Reviewed-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>