test: align ec_pub public keyfile with its ec_prv.sec1 counterpart

This change affects:
- both PEM and DER files, since they contain the same public key
  only in different formats
- "ec_pub.comp.pem" since it's the same as "ec_pub.pem" but in
  compressed format

The makefile was also updated accordingly to reflect these
dependencies.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/data_files/ec_pub.pem b/tests/data_files/ec_pub.pem
index d677d27..d54dc94 100644
--- a/tests/data_files/ec_pub.pem
+++ b/tests/data_files/ec_pub.pem
@@ -1,4 +1,4 @@
 -----BEGIN PUBLIC KEY-----
-MEkwEwYHKoZIzj0CAQYIKoZIzj0DAQEDMgAEvHl9s65/COw9SWtPtBGz9iClWKUB
-4CItCM/g3Irsixp78kvpKVHMW6G+uyR0kJrg
+MEkwEwYHKoZIzj0CAQYIKoZIzj0DAQEDMgAEUXW83zCjcPOdU5PmEnKI2AFntfS0
+t3bGdPfG81S30iQGLB9oVLWnrw/leOryWPAn
 -----END PUBLIC KEY-----