Vulkan: Fix rendering to RGB external images Based on the provided usage flags, the texture's image access mode is updated to be renderable. Bug: chromium:1266094 Change-Id: I5d092a2786fc12537ef0ad1f224137cc1fd8f864 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3270980 Reviewed-by: Craig Stout <cstout@google.com> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>