Fix event timing data for CUDA
Fix event timing data for CUDA

In contrast to start and end, time_submit is not based on a CUDA event
and therefore sometimes has a time stamp that is *after* start and end.

franz/pocl,pocl/pocl,pocl/pocl,pocl/pocl,franz/pocl,franz/pocl,Oblomov/pocl,franz/pocl,Oblomov/pocl,franz/pocl,Oblomov/pocl,pocl/pocl,pocl/pocl,Oblomov/pocl,Oblomov/pocl