asm: assembly code for pixel_sad_16x32
asm: assembly code for pixel_sad_16x64
primitives: fix ordering of LUMA_4x16 LUMA_16x4 to match other AMP partitions

This also fixes the testbench to properly represent 16x4 and 4x16 partition
primitives
Cleanups: Replacing Ushort with uint16_t