Vulkan: request coherent memory for StagingImage Otherwise vkInvalidateMappedMemoryRanges is needed, if allocated memory is not coherent, which was happening on Nexus 5X and was caught by validation layers. BUG=angleproject:2314 TEST=all angle_end2end_tests pass on Nexus 5X Change-Id: I008aae45b99c6ca87029ff1614913fae32f66ec3 Reviewed-on: https://chromium-review.googlesource.com/900203 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>