benchmarks/gem_exec_nop: Convert to running for a fixed time

Like the previous patch to gem_exec_ctx, retrict gem_exec_nop to running
for a fixed length of time, rather than over a range of different
execution counts. In order to retain some measurement of that range,
allow measuring individual execution versus continuous dispatch.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
1 file changed