Remove memcpy() in handle_inter_mode() filter selection.

Encode time of first 50 frames of bus (speed 0) @ 1500kbps goes from
2min4.9 to 2min3.1, i.e. a 1.4% speedup overall.

Change-Id: Ibe8b08d159797504c5d0c5122de1b6da3b6595e0