perf tests: Introduce iterator function for tests

perf tests: Introduce iterator function for tests

In preparation for introducing more arrays of tests, e.g. "arch tests"
(architecture-specific tests), abstract the code to iterate over the
list of tests into a helper function.

This way, code that uses a 'struct test' doesn't need to worry about how
the tests are grouped together and changes to the list of tests doesn't
require changes to the code using it.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
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/r/1441479742-15402-2-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>