i965: fix cycle estimates when there's a pipeline stall

i965: fix cycle estimates when there's a pipeline stall

The issue time for an instruction is how many cycles it takes to
actually put it into the pipeline. If there's a pipeline stall that
causes the instruction to be delayed, we should first take that into
account to figure out when the instruction would start executing and
*then* add the issue time. The old code had it backwards, and so we
would underestimate the total time whenever we thought there would be a
pipeline stall by up to the issue time of the instruction.

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