mmx/sse2: Use SIMPLE_NEAREST_FAST_PATH macro

mmx/sse2: Use SIMPLE_NEAREST_FAST_PATH macro

There is some reordering, but the only significant thing to ensure that
the same routine is chosen is that a COVER fast path for a given
combination of operator and source/destination pixel formats must
precede all the variants of repeated fast paths for the same
combination. This patch (and the other mmx/sse2 one) still follows that
rule.

I believe that in every other case, the set of operations that match any
pair of fast paths that are reordered in these patches are mutually
exclusive. While there will be a very subtle timing difference due to
the distance through the table we have to search to find a match
(sometimes faster, sometime slower) there is no evidence that the tables
have been carefully ordered by frequency of occurrence - just for ease
of copy-and-pasting.

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>