hevc/mvs: simplify derive_temporal_colocated_mvs

cherry picked from commit def7db60966765f4687250d766b40dbcf0f7e503

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
hevc/mvs: remove same prediction block

cherry picked from commit 1206262ba1ef810328cadce99d5cdc0bf9285e4d

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>