add 64-bit version of "mul_hi"

add 64-bit version of "mul_hi"

passed piglit test cases:
  piglit/framework/../bin/cl-program-tester generated_tests/cl/builtin/int/builtin-long-mul_hi-1.0.generated.cl
  piglit/framework/../bin/cl-program-tester generated_tests/cl/builtin/int/builtin-ulong-mul_hi-1.0.generated.cl

version 2:
  temp flag register is allocated by RA

version 3:
  divide subnr of flag register by typesize

version 4:
  fix a typo

Signed-off-by: Homer Hsing <homer.xing@intel.com>
Reviewed-by: "Song, Ruiling" <ruiling.song@intel.com>