Add ECDSA-P256 key in PKCS#8 format

utzig · d3zd3z · commit 90abedc7528e · 2019-01-18T09:44:48.000-07:00
The ring crypto library used by the simulator only accepts PEM keys in
PKCS#8 format; this provides a conversion of the original bundled key.

```
$ openssl pkcs8 -topk8 -nocrypt -in ../root-ec-p256.pem -out ../root-ec-p256-pkcs8.pem
```

Signed-off-by: Fabio Utzig &lt;utzig@apache.org&gt;
diff --git a/root-ec-p256-pkcs8.pem b/root-ec-p256-pkcs8.pem
@@ -0,0 +1,5 @@
+-----BEGIN PRIVATE KEY-----
+MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg15jVL4MBJDvTVCt+
+Ve1MdGEZALD5UFqCT+Ho7AY7z/GhRANCAAQqy0A86P7tW6RJlaGpHa7o274ZN80U
++y8kVzfllTmI2ZS51lrr183VMIrW/kiySmqBDuXwfYtoNMw6avxTjvrB
+-----END PRIVATE KEY-----
