Originally, this field was intended for determining if the given
instruction acted per-component or if it had mismatching source and
destination sizes that would have to be interpreted specially.  However, we
can easily derive this from output_size == 0, so it's not really that
useful.  Also, the values we were setting in nir_opcodes.h for this field
were completely bogus and it was never used.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>