testcases: sample static testcase to run checkpatch on the source

This is a sample static testcase (so it needs no target machine) to
run checkpatch as a testcase and produce output only if it fails.

Change-Id: I055c0125ac785058e101faa68eb5aaff9f7caf16
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>