save all registers in avx quantize
save all registers in avx quantize

cglobal declaration only saved 7 of the required 9 values.

Credits to nevcairiel for the proposed fix:
https://forum.doom9.org/showthread.php?p=1851389#post1851389

BUG=aomedia:2145

Change-Id: Ibf1e174246ef8dade816b46b44a13c8c8c575bd1

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