Fixed a few things related to FramebufferTextureLayer:
- Added layer validation to make sure it does not exceed
  the size of the 3D texture's or 2D array's depth.
- Fixed frambuffer target / texture target confusion.
- Removed bad validation.
- Fixed last 2 arguments of set[insert type]Buffer calls
  (layer and level) which were inverted.

Change-Id: Ie1f2cb595d8b9abfee27bcf834c535f7e023e3ee
Reviewed-on: https://swiftshader-review.googlesource.com/4343Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>