uboot-imx

MLK-22357-2 sdp/fastboot: Add board_usb_gadget_port_auto() to autodetect the connected usb port

On imx8 platform, the usb2 and usb3 ports are both supported. Which
means we can use usb2(ci_udc_otg) and usb3(cdns3_generic_peripheral)
gadget driver to run sdp/fastboot/ums at the same time.

For sdp and the fastboot that runs automatically when uboot starts,
board_usb_gadget_port_auto() is added to autodetect usb port, this
means that we don't have to specify which USB port should be used to
download in code, now we can just connect either usb port then it
will download automatically.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>