Set min_block_size for aq_mode=3 to 8x8.
Set min_block_size for aq_mode=3 to 8x8.

For real-time mode under cbr, this increases the gain (5-10%)
for speed 5 (none/little change for 6), on vc-clips.

Change-Id: I9b38beeb3c820de22c43a0ba53a9456168dd24ba

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