arm: Remove edminiv2 board and orion5x support

This board has not been converted to CONFIG_DM_MMC by the deadline.
Remove it.  As this is the last orion5x platform, remove that support as
well.

Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Stefan Roese <sr@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>