pw: Update to more recent version

- A patch is applied to compile with cpp check and other specificities
of the Open IoT SDK.
- A function to force linkage between backends/modules has been added.

Co-authored-by: Chris Swinchatt <christopher.swinchatt@arm.com>
Co-authored-by: Vincent Coubard <vincent.coubard@arm.com>
Signed-off-by: Vincent Coubard <vincent.coubard@arm.com>