Rearrange self-guided filter for vectorization
Rearrange self-guided filter for vectorization

By rearranging the order of operations, we can ensure that all
intermediate values fit into 32 bits. This will help when we
vectorize the self-guided filter.

Results in the noise range.

Change-Id: Ic0c73613882bd103c4e8e57a0155b3132672ae04

luctrudeau/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,smarter/aom,smarter/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,luctrudeau/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom,smarter/aom