smdkc100: Remove legacy non-DM_ETH code

Now that we are about to enable DM_ETH by default, remove legacy code.

Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>