arm: mvebu: Disable ATAGs support on some platforms

These platforms never had to support an ATAGs-based Linux Kernel, so
remove the options.

Cc: Stefan Roese <sr@denx.de>
Cc: Marek Behún <marek.behun@nic.cz>
Signed-off-by: Tom Rini <trini@konsulko.com>
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I'm assuming, please correct me if I'm wrong.