i965/nir/vec4: Implement multiplication
i965/nir/vec4: Implement multiplication

Implementation based on the vec4_visitor IR implementation
for the operations ir_binop_mul and ir_binop_imul_high.

Adds NIR ALU operations:
   * nir_op_fmul
   * nir_op_imul
   * nir_op_imul_high
   * nir_op_umul_high

Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler