virgl: enable FBFETCH if virglrenderer supports it

This fixes the following dEQP-GLES31 cases from NotSupported to
Pass for me:

- dEQP-GLES31.functional.blend_equation_advanced.state_query.*
- dEQP-GLES31.functional.blend_equation_advanced.basic.*
- dEQP-GLES31.functional.blend_equation_advanced.srgb.*
- dEQP-GLES31.functional.blend_equation_advanced.msaa.*
- dEQP-GLES31.functional.blend_equation_advanced.barrier.*
- dEQP-GLES31.functional.draw_buffers_indexed.overwrite_*advanced_blend_eq*
- dEQP-GLES31.functional.state_query.indexed.blend_equation_advanced_*
- dEQP-GLES31.functional.debug.negative_coverage.*.advanced_blend.*

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/gallium/drivers/virgl/virgl_hw.h

@@ -209,6 +209,7 @@ enum virgl_formats {
 #define VIRGL_CAP_COMPUTE_SHADER       (1 << 7)
 #define VIRGL_CAP_FB_NO_ATTACH         (1 << 8)
 #define VIRGL_CAP_ROBUST_BUFFER_ACCESS (1 << 9)
+#define VIRGL_CAP_TGSI_FBFETCH         (1 << 10)
 
 #define VIRGL_BIND_DEPTH_STENCIL (1 << 0)
 #define VIRGL_BIND_RENDER_TARGET (1 << 1)

src/gallium/drivers/virgl/virgl_screen.c

@@ -229,6 +229,8 @@ virgl_get_param(struct pipe_screen *screen, enum pipe_cap param)
       return vscreen->caps.caps.v2.capability_bits & VIRGL_CAP_FB_NO_ATTACH;
    case PIPE_CAP_ROBUST_BUFFER_ACCESS_BEHAVIOR:
       return vscreen->caps.caps.v2.capability_bits & VIRGL_CAP_ROBUST_BUFFER_ACCESS;
+   case PIPE_CAP_TGSI_FS_FBFETCH:
+      return vscreen->caps.caps.v2.capability_bits & VIRGL_CAP_TGSI_FBFETCH;
    case PIPE_CAP_TEXTURE_GATHER_SM5:
    case PIPE_CAP_BUFFER_MAP_PERSISTENT_COHERENT:
    case PIPE_CAP_FAKE_SW_MSAA:
@@ -268,7 +270,6 @@ virgl_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_TGSI_ARRAY_COMPONENTS:
    case PIPE_CAP_TGSI_CAN_READ_OUTPUTS:
    case PIPE_CAP_GLSL_OPTIMIZE_CONSERVATIVELY:
-   case PIPE_CAP_TGSI_FS_FBFETCH:
    case PIPE_CAP_TGSI_MUL_ZERO_WINS:
    case PIPE_CAP_INT64:
    case PIPE_CAP_INT64_DIVMOD: