nv50/ir: fix memory corruption when spilling and redoing RA

When RA fails, and we spill, we have to clean everything up before doing
RA again. We were forgetting to reset the hi/lo linked lists - at
least the hi list is guaranteed to still have pointers to now-deleted
RIG nodes.

Signed-off-by: Karol Herbst <nouveau@karolherbst.de>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org

src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp

@@ -1544,6 +1544,9 @@ GCRA::cleanup(const bool success)
 
    delete[] nodes;
    nodes = NULL;
+   hi.next = hi.prev = &hi;
+   lo[0].next = lo[0].prev = &lo[0];
+   lo[1].next = lo[1].prev = &lo[1];
 }
 
 Symbol *