cmd: usb: check if_type before using this device

cmd: usb: check if_type before using this device

For legacy usb storage driver, USB_MAX_STOR_DEV is defined as 7.
If we only have one usb disk on board, `usb dev 0` is ok.
But if `usb dev 1`, still ok, then `usb read xxx` will trigger
system fault and reboot.

So check if_type before using this device.

Signed-off-by: Peng Fan <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Hans de Goede <[email protected]>
Cc: Bin Meng <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: Stefan Roese <[email protected]>
Cc: Marcel Ziswiler <[email protected]>
Cc: Peng Fan <[email protected]>
Cc: Stephen Warren <[email protected]>