intel/compiler: use bitset instead of opencoding a 32-bit bitset. (v2)

intel/compiler: use bitset instead of opencoding a 32-bit bitset. (v2)

In the future I want to expand this to 128-bits, for vec16 support, so
lets just put the code in place to use bitset ranges now.

v2: just declare the bitset to be the max of what we should ever see
and change assert to reflect it.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>