i965: fix brw_saturate_immediate() for doubles
i965: fix brw_saturate_immediate() for doubles

v2 (Sam):
  - Mark 'size' as const (Topi).
  - Add comment to explain that we do copies 64-bits regardless of the
    type (Topi)

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler