mlxsw: core_acl_flex_keys: Fill blocks with high entropy first

The previous patches prepared the code to allow separating between
choosing blocks and filling blocks.

Do not add blocks as part of the loop that chooses them. When all the
required blocks are set in the bitmap 'chosen_blocks_bm', start filling
blocks. Iterate over the bitmap twice - first add only blocks that are
marked with 'high_entropy' flag. Then, fill the rest of the blocks.

The idea is to place key blocks with high entropy in blocks 0 to 5. See
more details in previous patches.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>