2D array textures aren't supposed to filter between layers and the
computation used in the filtering code is meant to work with 3D
textures, not 2D array textures. The 2D array textures now use the
2D texture path instead of the 3D texture path to solve this issue.

Change-Id: Iea8fcfe67cce7ae70e39081af07e67fa59b268ff
Reviewed-on: https://swiftshader-review.googlesource.com/4690Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>