Vulkan: Assign XFB location first then assign varying location Varying location is determined based on XFB location. If the transform feedback stage is Vertex, there is no problem. But if the transform feedback stage is GS or TES, previous implementation can cause shader interface mismatch. Bug: angleproject:5557 Test: KHR-GLES32.core.tessellation_shader.tessellation_control_to_tessellation_evaluation.gl_in Change-Id: I1ecc7913a178c9e674307c528d1bdf13aabcb665 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2784713 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Mohan Maiya <m.maiya@samsung.com>