nir/opcodes: Add a helper function to generate reduce opcodes

nir/opcodes: Add a helper function to generate reduce opcodes

Adds binop_reduce_all_sizes which generates both 1-bit and 32-bit
versions of the reduce operation. This reduces the code duplication a
bit and will make it easier to later add 16-bit versions as well.

Reviewed-by: Rob Clark <robdclark@gmail.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>