optee-examples.bb: add recipe for optee examples

This has moved from meta-linaro to meta-arm as this
is the new place for general recipes for Arm arch
and has a mailing list for external contributors.

Change-Id: I75de7398e9247c8a329f50292f912b7787ead372
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>