usb: dwc2: gadget: Repair DSTS register decoding

The "enumspd" field is located in register DSTS[2:1], but the code
which checks the bitfield does not shift the value accordingly. This
in turn causes incorrect detection of gadget link partner speed in
dwc2_hsotg_irq_enumdone() .

Shift the value accordingly to fix the problem with speed detection.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>