nir: remove dead code from copy_prop_vars

When copy_prop_vars also took care of dead write handling, intrin was
used as part of store_to_entry.  Now it isn't, so this assignment
isn't used really used.  Add a comment clarifying what happens to
intrin.

Fixes: 4dfa7adc100 "nir: Remove handling of dead writes from copy_prop_vars"
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
1 file changed