linux-imx

perf trace: Remove thread_trace->exit_time

Not used at all, we need just the entry_time to calculate the syscall
duration.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-js6r09zdwlzecvaei7t4l3vd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>