utils: Remove tinyfdt.c

tinyfdt.c was originally added to provide a minimal implementation of
fdt parsing. However, we have already included libfdt in OpenSBI for
more complicated operations.

Remove tinfdt and replace its functiolity using libfdt.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Acked-by: Anup Patel <anup.patel@wdc.com>