data_files: remove duplicate of ec_256 files and regorganize

- there was already a SEC1 formatted EC file for secp256r1 so
  ec_256_prv.sec1.der was useless;
- all other ec_256_[pub|priv] files should be generated starting from
  ec_256_prv.pem

Signed-off-by: Valerio Setti <vsetti@baylibre.com>

data_files/Makefile

@@ -1759,10 +1759,6 @@ ec_256_pub.comp.pem: ec_256_pub.pem
 	$(OPENSSL) ec -pubin -in $< -out $@ -conv_form compressed
 all_final += ec_256_pub.comp.pem
 
-ec_256_pub.der: ec_256_prv.sec1.der
-	$(OPENSSL) ec -in $< -outform DER -pubout -out $@
-all_final += ec_256_pub.der
-
 ec_384_pub.comp.pem: ec_384_pub.pem
 	$(OPENSSL) ec -pubin -in $< -out $@ -conv_form compressed
 all_final += ec_384_pub.comp.pem
@@ -1850,17 +1846,13 @@ ec_prv.sec1.der: ec_prv.sec1.pem
 	$(OPENSSL) pkey -in $< -out $@ -outform DER
 all_final += ec_prv.sec1.der
 
-ec_256_prv.sec1.der:
-	$(OPENSSL) ecparam -name prime256v1 -genkey -outform DER -noout -out $@
-all_final += ec_256_prv.sec1.der
+ec_256_prv.der: ec_256_prv.pem
+	$(OPENSSL) pkey -in $< -out $@ -outform DER
+all_final += ec_256_prv.pem
 
-ec_256_prv.sec1.pem: ec_256_prv.sec1.der
-	$(OPENSSL) ec -in $< -out $@ -outform PEM
-all_final += ec_256_prv.sec1.pem
-
-ec_256_prv.sec1.comp.pem: ec_256_prv.sec1.der
-	$(OPENSSL) ec -in $< -conv_form compressed -outform PEM -out $@
-all_final += ec_256_prv.sec1.comp.pem
+ec_256_pub.der: ec_256_prv.pem
+	$(OPENSSL) pkey -in $< -outform DER -pubout -out $@
+all_final += ec_256_pub.der
 
 ec_256_long_prv.der: ec_256_long_prv.pem
 	$(OPENSSL) pkey -in $< -out $@ -outform DER