nouveau: 3d textures are unsupported, limit 3d levels to 1

Ideally there would be a swrast fallback, but the driver isn't ready for
that. This should avoid crashes if someone tries to use 3d textures
though.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Cc: mesa-stable@lists.freedesktop.org
(cherry picked from commit 5524af8136)

src/mesa/drivers/dri/nouveau/nouveau_context.c

@@ -189,6 +189,9 @@ nouveau_context_init(struct gl_context *ctx, gl_api api,
 	ctx->Extensions.NV_texture_env_combine4 = true;
 	ctx->Const.MaxColorAttachments = 1;
 
+	/* This effectively disables 3D textures */
+	ctx->Const.Max3DTextureLevels = 1;
+
 	return GL_TRUE;
 }