The layerCount for 3D texture and 2DArray should be 1 if it does not
have layers.

Bug: b/170657065
Change-Id: I974ddda7c0eaa92da8033f15c682820e3d4eb32a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2466616Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Charlie Lao <cclao@google.com>