Vulkan spec says that image layout is not counted toward render pass
compatibility:

"Two render passes are compatible if their corresponding color, input,
resolve, and depth/stencil attachment references are compatible and if
they are otherwise identical except for: Initial and final image layout
in attachment descriptions Image layout in attachment references"

This CL removes the depth stencil access mode information out of
RenderPassDesc structure. It is essentially partially reverted the
change from crrev.com/c/2354280

Bug: b/170134600
Change-Id: Iada4d89c3249489b47db3046952e7cb10f252891
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2451597
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>