test: cmd: fdt: Test fdt move

Add 'fdt move' test which works as follows:
- Create simple FDT, map it to sysmem
- 'move' the FDT into new zeroed out sysmem location
- Verify newly active FDT is in the new location
- Compare both locations

The test case can be triggered using:
"
./u-boot -Dc 'ut fdt'
"
To dump the full output from commands used during test, add '-v' flag.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>