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>

arch/arm/dts/imx7d-sdb-u-boot.dtsi

 &fec2 {
 	status = "disable";
 };
+
+&usbotg1 {
+	dr_mode = "peripheral";
+};