toradex: common: set board-rev and product-id

toradex: common: set board-rev and product-id

Set board revision and Toradex product ID as device tree property.
This transfers the Toradex configblock information to Linux user-
space, where it can be read conviniently through the proc file
system files:
- /proc/device-tree/serial-number
- /proc/device-tree/toradex,board-rev
- /proc/device-tree/toradex,product-id

In case the Toradex config block is missing or corrupted, the
device tree properties won't be created by the boot loader and
hence those file won't exist in that case.