mx7dsabre: Fix usbtog probe when use dfu or ums

Before:
=> ums 0 mmc 0
UMS: LUN 0, dev 0, hwpart 0, sector 0x0, count 0x1dacc00
usb dr_mode not found
CTRL+C - Operation aborted
=> dfu 0 mmc 0
usb dr_mode not found

After :
=> ums 0 mmc 0
UMS: LUN 0, dev 0, hwpart 0, sector 0x0, count 0x1dacc00
=> dfu 0 mmc 0

Signed-off-by: Joris Offouga <offougajoris@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
1 file changed