Refactor: Extract util functions for jnt convolve
Refactor: Extract util functions for jnt convolve

1. unpack_weights_avx2
2. load_line2_avx2

Change-Id: I8911da666602d400474b4d624f414cb4231143fb

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom