selftests: add kselftest framework for uniform test reporting

selftests: add kselftest framework for uniform test reporting

Add kselftest framework for tests to use. This is a light
weight framework provides a set of interfaces to report test
results. Tests can use these interfaces to report pass, and
fail cases as well as when failure is due to configuration
problems such as missing modules, or when a test that is should
fail, fails as expected, and a test that should fail, passes.
The framework uses POSIX standard return codes for reporting
results to address the needs of users that want to run the kernel
selftests from their user-space test suites and want to know why a
test failed. In addition, the framework includes interfaces to use
to report test statistics on number of tests passed and failed.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>