nir: Initialize lower_flrp_progress everywhere
I don't know why I thought NIR_PASS always set the progress variable. Derp.
Fixes: d41cdef2 ("nir: Use the flrp lowering pass instead of nir_opt_algebraic")
Coverity CID: 1444996
Coverity CID: 1444995
Coverity CID: 1444994
Coverity CID: 1444993
Coverity CID: 1444991
Coverity CID: 1444989
Edited by Ian Romanick