radv: do not expose NV DGC extensions on GFX6-7

These extensions were experimental and only exposed with radv_dgc=true
for vkd3d-proton. Only two games require DGC (Starfield and Halo
Infinite) and both also require sparse support which GFX6-7 can't
support.

GFX6-7 support is also mostly broken because IB2 can't be used when
indirect draw packets are used and RADV uses that to preprocess IBO.
Also with the EXT, indirect draws are more common and can't be
supported.

Everything could work with a bunch of time and workarounds but I don't
think it's worth the effort given there is no real use.

Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31491>

src/amd/vulkan/radv_physical_device.c

@@ -747,8 +747,8 @@ radv_physical_device_get_supported_extensions(const struct radv_physical_device
       .INTEL_shader_integer_functions2 = true,
       .MESA_image_alignment_control = pdev->info.gfx_level >= GFX9 && pdev->info.gfx_level <= GFX11_5,
       .NV_compute_shader_derivatives = true,
-      .NV_device_generated_commands = instance->drirc.enable_dgc,
-      .NV_device_generated_commands_compute = instance->drirc.enable_dgc,
+      .NV_device_generated_commands = pdev->info.gfx_level >= GFX8 && instance->drirc.enable_dgc,
+      .NV_device_generated_commands_compute = pdev->info.gfx_level >= GFX8 && instance->drirc.enable_dgc,
       /* Undocumented extension purely for vkd3d-proton. This check is to prevent anyone else from
        * using it.
        */

src/util/driconf.h

@@ -694,7 +694,7 @@
 
 #define DRI_CONF_RADV_DGC(def) \
    DRI_CONF_OPT_B(radv_dgc, def, \
-                  "Expose an experimental implementation of VK_NV_device_generated_commands")
+                  "Expose an experimental implementation of VK_NV_device_generated_commands on GFX8+")
 
 #define DRI_CONF_RADV_FLUSH_BEFORE_QUERY_COPY(def) \
   DRI_CONF_OPT_B( \