Output the map from IR reg to ASM reg

Output the map from IR reg to ASM reg

It is hard to guess the meaning of
  "mul(8) g10<1>d g0.6<0,1,0>d g3.2<0,1,0>d"
if you don't know the IR reg num of "g10" etc.

Now we can output the map from IR reg to ASM reg, such as
  "%0 g10.0D"
  "%1 g0.6D"
  "%2 g3.2D"
So you know the meaning is
  "mul %0 %1 %2"

By default, not output those message.
You can turn on by BVAR "OCL_OUTPUT_REG_ALLOC".

Signed-off-by: Homer Hsing <homer.xing@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>