Encapsulation control flags are currently not used anywhere,
so all flags are currently unsupported by all drivers.

This patch adds validation of this assumption, so that
encapsulation flags may be used in the future.

In case any encapsulation control flags are masked,
flow_rule_match_has_enc_control_flags() sets a NL extended
error message, and we return -EOPNOTSUPP.

Only compile tested.
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/20240609173358.193178-6-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>