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>