Reorder linalg.conv indexing_maps loop order

Change the indexing map to iterate over the (b, x0, x1, z0, z1, q, k) instead of (b, x0, x1, k, q, z0, z1) to evaluate the convolution expression:
Y[b, x0, x1, k] = sum(W[z0, z1, q, k] * X[b, x0 + z0, x1 + z1, q], z0, z1, q)

This allows llvm auto vectorize to work and has better locality resulting significant performance improvments

Differential Revision: https://reviews.llvm.org/D87781