tools/perf/build: Harmonize the style of the feature testcases

tools/perf/build: Harmonize the style of the feature testcases

The various testcases used different styles, which was not really
visible as long as they hid in feature-tests.mak. Now that they
are out in the open make them prettier.

( Also delete the leftover, empty feature-tests.mak file. )

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-drDWk8xltndjdsespzjbhu6w@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>