radeonsi: add AMD_DEBUG=nogfx for testing

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>

src/gallium/drivers/radeonsi/si_pipe.c

@@ -90,6 +90,7 @@ static const struct debug_named_value debug_options[] = {
 	{ "zerovram", DBG(ZERO_VRAM), "Clear VRAM allocations." },
 
 	/* 3D engine options: */
+	{ "nogfx", DBG(NO_GFX), "Disable graphics. Only multimedia compute paths can be used." },
 	{ "alwayspd", DBG(ALWAYS_PD), "Always enable the primitive discard compute shader." },
 	{ "pd", DBG(PD), "Enable the primitive discard compute shader for large draw calls." },
 	{ "nopd", DBG(NO_PD), "Disable the primitive discard compute shader." },
@@ -943,6 +944,9 @@ radeonsi_screen_create_impl(struct radeon_winsys *ws,
 	sscreen->debug_flags |= debug_get_flags_option("AMD_DEBUG",
 						       debug_options, 0);
 
+	if (sscreen->debug_flags & DBG(NO_GFX))
+		sscreen->info.has_graphics = false;
+
 	/* Set functions first. */
 	sscreen->b.context_create = si_pipe_create_context;
 	sscreen->b.destroy = si_destroy_screen;

src/gallium/drivers/radeonsi/si_pipe.h

@@ -175,6 +175,7 @@ enum {
 	DBG_ZERO_VRAM,
 
 	/* 3D engine options: */
+	DBG_NO_GFX,
 	DBG_ALWAYS_PD,
 	DBG_PD,
 	DBG_NO_PD,