The empire-electronix-d709 does not have an emmc, it uses nand, the
mmc2 node in the dts comes from a copy and paste error from the
inet98fv2 dts, remove it.

While at it also do s/inet98fv2/d709/ to fix some other copy/paste
leftovers.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>