r600/sfn: Use register keep-alive also when scanning the shader

Temporaries don't appear in the mapping, so they are not in the initial
register list.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7142>
2 files changed