Tests that only make sense for some architectures currently live in
the same place as the generic tests. Move out the x86-specific tests
into tools/perf/arch/x86/tests and define an 'arch_tests' array, which
is the list of tests that only apply to the build architecture.

The main idea is to encourage developers to add arch tests to build
out perf's test coverage, without dumping everything in
tools/perf/tests.
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kanaka Juvva <kanaka.d.juvva@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vikas Shivappa <vikas.shivappa@intel.com>
Cc: Vince Weaver <vince@deater.net>
Link: http://lkml.kernel.org/n/tip-p4uc1c15ssbj8xj7ku5slpa6@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>