Replace the copyright notice in header comments by an equivalent
SPDX-License-Identifier string. Drop a following empty line if at the
bottom of the comment. Leave any other header comment content in place.
This also fixes for an incomplete notice in examples/nft-ruleset-get.c
since commit c335442eefcca ("src: incorrect header refers to GPLv2
only").
Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
e944a0afbc