configs/olimex_a20_olinuxino_lime2: use NEON+VFPv4 as FPU strategy

Allwinner A20 supports NEON+VFPv4 so let's enable instead of the default
VFPv4-D16.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>