usb: gadget: atmel_usba_udc: Expose correct device speed

Following changes that appeared in lk 4.0.0, the gadget udc driver for
some ARM based Atmel SoCs (e.g. at91sam9x5 and sama5d3 families)
incorrectly deduced full-speed USB link speed even when the hardware
had negotiated a high-speed link. The fix is to make sure that the
UDPHS Interrupt Enable Register value does not mask the SPEED bit
in the Interrupt Status Register.

For a mass storage gadget this problem lead to failures when the host
had a USB 3 port with the xhci_hcd driver. If the host was a USB 2
port using the ehci_hcd driver then the mass storage gadget worked
(but probably at a lower speed than it should have).

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: <stable@vger.kernel.org> #4.0+
Fixes: 9870d895 ("usb: atmel_usba_udc: Mask status with enabled irqs")
Signed-off-by: Felipe Balbi <balbi@ti.com>