flow_dissector: set encapsulated control flags from tun_flags

flow_dissector: set encapsulated control flags from tun_flags

Set the new FLOW_DIS_F_TUNNEL_* encapsulated control flags, based
on if their counter-part is set in tun_flags.

These flags are not userspace visible yet, as the code to dump
encapsulated control flags will first be added, and later activated
in the following patches.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Tested-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/20240713021911.1631517-8-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>