test: check pkparse with compressed ec

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/data_files/ec_521_prv.comp.pem b/tests/data_files/ec_521_prv.comp.pem
new file mode 100644
index 0000000..314c393
--- /dev/null
+++ b/tests/data_files/ec_521_prv.comp.pem
@@ -0,0 +1,6 @@
+-----BEGIN EC PRIVATE KEY-----
+MIGYAgEBBEIBsbatB7t55zINpZhg6ijgVShPYFjyed5mbgbUNdKve9oo2Z+ke33Q
+lj4WsAcweO6LijjZZqWC9G0Z/5XfOtloWq6gBwYFK4EEACOhRgNEAAMAHeFC1U9p
+6wOO5LevnTygdzb9nPcZ6zVNaYee5/PBNvsPv58I+Gvl+hKOwaBR0+bGQ+ha2o/6
+zzZjwmC9LIRLb1Y=
+-----END EC PRIVATE KEY-----