Backend: Add sel ir output for MATH function
Backend: Add sel ir output for MATH function

We only output MATH function before, now we can know which math
function is it.

Signed-off-by: Pan Xiuli <e5a665b1e626c5dc0826076a8b5a209eb48bf6ee@intel.com>
Reviewed-by: Yang Rong <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>

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