radeonsi: remove AMD_DEBUG=nogfx

it doesn't work - it uses the CDNA codepath for preamble, which surely
hangs on non-CDNA

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26055>

docs/envvars.rst

@@ -1482,8 +1482,6 @@ RadeonSI driver environment variables
       Check VM faults and dump debug info.
    ``reserve_vmid``
       Force VMID reservation per context.
-   ``nogfx``
-      Disable graphics. Only multimedia compute paths can be used.
    ``nongg``
       Disable NGG and use the legacy pipeline.
    ``nggc``

src/gallium/drivers/radeonsi/si_pipe.c

@@ -90,7 +90,6 @@ static const struct debug_named_value radeonsi_debug_options[] = {
    { "noefc", DBG(NO_EFC), "Disable hardware based encoder colour format conversion."},
 
    /* 3D engine options: */
-   {"nogfx", DBG(NO_GFX), "Disable graphics. Only multimedia compute paths can be used."},
    {"nongg", DBG(NO_NGG), "Disable NGG and use the legacy pipeline."},
    {"nggc", DBG(ALWAYS_NGG_CULLING_ALL), "Always use NGG culling even when it can hurt."},
    {"nonggc", DBG(NO_NGG_CULLING), "Disable NGG culling."},
@@ -1224,9 +1223,6 @@ static struct pipe_screen *radeonsi_screen_create_impl(struct radeon_winsys *ws,
       return NULL;
    }
 
-   if (sscreen->debug_flags & DBG(NO_GFX))
-      sscreen->info.has_graphics = false;
-
    if ((sscreen->debug_flags & DBG(TMZ)) &&
        !sscreen->info.has_tmz_support) {
       fprintf(stderr, "radeonsi: requesting TMZ features but TMZ is not supported\n");

src/gallium/drivers/radeonsi/si_pipe.h

@@ -229,7 +229,6 @@ enum
    DBG_NO_EFC,
 
    /* 3D engine options: */
-   DBG_NO_GFX,
    DBG_NO_NGG,
    DBG_ALWAYS_NGG_CULLING_ALL,
    DBG_NO_NGG_CULLING,