i965/vec4: extend the DWORD multiply DepCtrl restriction to all gen8 platforms
i965/vec4: extend the DWORD multiply DepCtrl restriction to all gen8 platforms

v2:
   - Add Broxton as Intel's internal PRMs says that it is needed (Matt).

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler