fdt: Update CRC check for rng-seed

Commit 428826f5 ("fdt: add support for rng-seed") moves of_fdt_crc32
from early_init_dt_verify() to early_init_dt_scan() since
early_init_dt_scan_chosen() may modify fdt to erase rng-seed.

However, arm and some other arch won't call early_init_dt_scan(), they
call early_init_dt_verify() then early_init_dt_scan_nodes().

Restore of_fdt_crc32 to early_init_dt_verify() then update it in
early_init_dt_scan_chosen() if fdt if updated.

Fixes: 428826f5 ("fdt: add support for rng-seed")
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Will Deacon <will@kernel.org>