x86/hevc: get rid off packusdw for ssse3 compatibility

cherry picked from commit df8ebe304df453f26c28ff8f11d607f49b90a4c2

Fixes out of array access
Fixes: asan_stack-oob_1046454_9_asan_stack-oob_15a9e7c_170_WP_MAIN10_B_Toshiba_3.bit

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
