Backend: Implement emitCalcTimestampInstruction in GenContext.
Backend: Implement emitCalcTimestampInstruction in GenContext.

We will maintain a real clock to record the real execute time
of the orginal code. We do not want to introduce overhead
because of adding the profiling instructions, so every time
we enter the proliling instructions block, we will calculate the
real time clock value and update the real clock, and when leave
this the proliling instructions block, we will record the time
stamp of that leave point.

Signed-off-by: Junyan He <8f73a735c668918c9613b750d3a88ebf2489599f@linux.intel.com>
Reviewed-by: Yang Rong <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>

wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet