benchmarks/gem_latency: Expose the workload factor
benchmarks/gem_latency: Expose the workload factor

Allow the user to select how many batches each producer submits before
waiting.

Signed-off-by: Chris Wilson <711c73f64afdce07b7e38039a96d2224209e9a6c@chris-wilson.co.uk>

tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools