vrend: Return EINVAL when switching context failed

This aligns the behavior of vrend_renderer_transfer_internal with
vrend_decode_ctx_submit_cmd.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Part-of: <https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/715>

.gitlab-ci/expectations/virt/piglit-virgl-gles-fails.txt

@@ -348,12 +348,6 @@ spec@arb_shader_image_load_store@host-mem-barrier@Pixel/RaW/full barrier test/64
 spec@arb_shader_image_load_store@host-mem-barrier@Pixel/RaW/one bit barrier test/16x16,Fail
 spec@arb_shader_image_load_store@host-mem-barrier@Pixel/RaW/one bit barrier test/4x4,Fail
 spec@arb_shader_image_load_store@host-mem-barrier@Pixel/RaW/one bit barrier test/64x64,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/full barrier test/16x16,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/full barrier test/4x4,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/full barrier test/64x64,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/one bit barrier test/16x16,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/one bit barrier test/4x4,Fail
-spec@arb_shader_image_load_store@host-mem-barrier@Pixel/WaW/one bit barrier test/64x64,Fail
 spec@arb_shader_image_load_store@host-mem-barrier@Texture fetch/RaW/full barrier test/16x16,Fail
 spec@arb_shader_image_load_store@host-mem-barrier@Texture fetch/RaW/full barrier test/4x4,Fail
 spec@arb_shader_image_load_store@host-mem-barrier@Texture fetch/RaW/full barrier test/64x64,Fail

src/vrend_renderer.c

@@ -8440,7 +8440,8 @@ static int vrend_renderer_transfer_internal(struct vrend_context *ctx,
    if (!info->box)
       return EINVAL;
 
-   vrend_hw_switch_context(ctx, true);
+   if (!vrend_hw_switch_context(ctx, true))
+      return EINVAL;
 
    assert(check_transfer_iovec(res, info));
    if (info->iovec && info->iovec_cnt) {