nir: Add algebraic optimizations for division and reciprocal.

nir: Add algebraic optimizations for division and reciprocal.

These also exist in opt_algebraic.cpp.

total NIR instructions in shared programs: 2011430 -> 2011211 (-0.01%)
NIR instructions in affected programs:     42221 -> 42002 (-0.52%)
helped:                                    198

total i965 instructions in shared programs: 6020553 -> 6020116 (-0.01%)
i965 instructions in affected programs:     84322 -> 83885 (-0.52%)
helped:                                     394
HURT:                                       1 (by 1 instruction)

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>