intel_gpu_top: account for time spent in syscalls
intel_gpu_top: account for time spent in syscalls

This allows intel_gpu_top to properly account for time spent inside system
calls. Effectively, with previous implementation, intel_gpu_top could
spent longer than 1s between consecutive measures. This attempts to
minimize the extra time spent while polling for data.

Signed-off-by: Eugeni Dodonov <8cab21ffd2ceb3ee06d75e34eb970dfea6bd7cc6@intel.com>

erikarn/intel-gpu-tools,ChrisCummins/intel-gpu-tools,tiagovignatti/intel-gpu-tools,dlespiau/checkmate-test-igt,yipdw/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,erikarn/intel-gpu-tools,ChrisCummins/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,rib/intel-gpu-tools,tiagovignatti/intel-gpu-tools,dlespiau/intel-gpu-tools,dlespiau/intel-gpu-tools,yipdw/intel-gpu-tools,rib/intel-gpu-tools,rib/intel-gpu-tools,tiagovignatti/intel-gpu-tools,dlespiau/checkmate-test-igt,ChrisCummins/intel-gpu-tools,yipdw/intel-gpu-tools,dlespiau/checkmate-test-igt,erikarn/intel-gpu-tools,ChrisCummins/intel-gpu-tools,yipdw/intel-gpu-tools,erikarn/intel-gpu-tools,rib/intel-gpu-tools,dlespiau/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools