usb: dwc2: Reorder AHBIDLE and CSFTRST in dwc2_core_reset()

According to the databook, the core soft reset should be done before
checking for AHBIDLE. The gadget version of core reset had it correct
but the hcd version did not. This fixes the hcd version.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>