Vulkan: Free 8 bits in RenderPassDesc These bits will be used in a follow up change to determine which color attachments need to take their value from a corresponding resolve attachment in an initial subpass. Bug: angleproject:4881 Change-Id: I76b6b3339fe209f93dd259ca087d84ecaa3004b6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2397205 Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>