In-tree objdump is too old for dump new elf headers. But if we use
make CROSS_TOOLCHAIN= and not specify CROSS_BINUTILS_PREFIX in env,
embed_mfs.sh cannot find the correct objdump. This patch just replaces using
of objdump with elfdump to collect needed information.
Later we may also put an ELFDUMP in CROSSENV and use it in embed_mfs.sh .