spl: fit: Make room in the FDT before applying overlays

spl: fit: Make room in the FDT before applying overlays

Make room in the FDT before applying the overlay, otherwise it may fail if
the overlay is big. As the exact added size is not known in advance, just
add the size of the overlay.
Move after the end of the application of the overlays, the resize  of the
FDT for the injection of the details on the loadables.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>