Vulkan: Fix use of uninitialized data in staged clears When depth/stencil data are staged, only the depthStencil field of VkClearValue is initialized. However, when comparing staged clears, memcmp is used which also compares the extra bytes in the aliasing color field. Bug: chromium:1144491 Change-Id: Ic384ba792e9fd199d8e9c3e534ccdc6ea65ee9b8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2517244 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>