Replace scatter scan 32x32 with HW friendly scan.

The first 240 coeff positions (15 top-left blocks) are scanned in the
same order as in scatter scan, after that the coeffs are scanned in
"block bands", each band at a time, all coeffs in one band before
moving on to the next band. This brings down the amount of 4x4 coeff
blocks that need to be buffered while scanning, from 15 blocks to 8 blocks.

Change-Id: I478a991d63c48bd5e64d36e59fed7a00c9a651ba