net/handshake: Add new parameter 'HANDSHAKE_A_ACCEPT_KEYRING'

Add a new netlink parameter 'HANDSHAKE_A_ACCEPT_KEYRING' to provide
the serial number of the keyring to use.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250701144657.104401-1-hare@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>