libseccomp: update to 2.5.1

libseccomp: update to 2.5.1

Release notes as per https://github.com/seccomp/libseccomp/releases/tag/v2.5.1:

Version 2.5.1 - November 20, 2020

    Fix a bug where seccomp_load() could only be called once
    Change the notification fd handling to only request a notification fd if
    the filter has a _NOTIFY action
    Add documentation about SCMP_ACT_NOTIFY to the seccomp_add_rule(3) manpage
    Clarify the maintainers' GPG keys

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>