uboot-phytec

imx: tpc70: Add board_boot_order() to distinguish between eMMC and SD boot

The TPC70 can boot from SD card (debug/development) and eMMC (production).
The board_boot_order() function provides a run time check for the device
from which one wants to boot (it is selected by GPIO pins setup).

Moreover, a fallback to SD card is provided if the detection is not
possible or working properly.

Signed-off-by: Lukasz Majewski <lukma@denx.de>