tools: ynl: remove __pycache__ during clean

Build process uses python to generate the user space code.
Remove __pycache__ on make clean.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools: ynl: add distclean to .PHONY in all makefiles

Donald points out most YNL makefiles are missing distclean
in .PHONY, even tho generated/Makefile does list it.

Suggested-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools: ynl: rename make hardclean -> distclean

The make target to remove all generated files used to be called
"hardclean" because it deleted files which were tracked by git.
We no longer track generated user space files, so use the more
common "distclean" name.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools: ynl: user space helpers

Add "fixed" part of the user space Netlink Spec-based library.
This will get linked with the protocol implementations to form
a full API.

Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>