sunxi: Imply fitImage support

Enable modern fitImage format on sunxi.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Tom Rini <trini@konsulko.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>