config: add am62x-lp-sk-dfu configuration
This allows to build special bootloader binaries which have dfu mode enabled. DFU allows board recovery via snagboot which is very useful for initial flashing or unbricking boards.
See: https://baylibre.pages.baylibre.com/ti/android/doc/am62x/android/dfu-recovery.html
Signed-off-by: Mattijs Korpershoek mkorpershoek@baylibre.com