openssh: share ed25519 keys
openssh: share ed25519 keys

We share SSH keys between multiple OS images via the /etc/natinst/share
mount point.  Currently, the dsa, ecdsa, and rsa keys are shared in this
manner; share the ed25519 keys as well.

Signed-off-by: Ben Shelton <873d2944fc7a954ed322314738197137e10de387@ni.com>
Reviewed-by: Ken Sharp <e6c8ad8f54d15df4645e8aaf3f7a209bc3688570@ni.com>
Reviewed-by: Joseph Hershberger <29dcc50cc0b9f222f8d3013ffae7ad988d7193bb@ni.com>
Reviewed-by: Rich Tollerton <67c688e7f7482ba5c4ebe3d70bc77594748182a6@ni.com>
---
Natinst-CAR-ID: 523823
Natinst-ReviewBoard-ID: 95472

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt