rdopt: move/remove 2d arrays in pick_inter_mode_sb
rdopt: move/remove 2d arrays in pick_inter_mode_sb

Two 2D arrays were passed to HandleInterMode and not used elsewhere.

One has been added to the HandleInterModeArgs struct to
simplify handle_inter_mode's signature and the the calling function.

The other has been unread since commit
beacb3ff79ad4ca563c7d154244307fcb944889e. That patch removed the
"skip_txfm optimization" but left the single_skippable array in place,
even though it was no longer read. Since the array's only usage has been
removed, this patch removes the variable outright.

Change-Id: I6e680a9ddc6f67961153819a62009751252757a8

luctrudeau/aom,GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,smarter/aom,smarter/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom