test_suite_pk: uniformly generate RSA and EC keys in pk_psa_sign()

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 702c23e..272e9f6 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -1862,8 +1862,7 @@
     if (PSA_KEY_TYPE_IS_RSA(psa_type)) {
         TEST_ASSERT(mbedtls_pk_setup(&pk,
                                      mbedtls_pk_info_from_type(MBEDTLS_PK_RSA)) == 0);
-        TEST_ASSERT(mbedtls_rsa_gen_key(mbedtls_pk_rsa(pk), mbedtls_test_rnd_std_rand, NULL,
-                                        bits, 3) == 0);
+        TEST_EQUAL(pk_genkey(&pk, bits), 0);
         TEST_EQUAL(mbedtls_rsa_set_padding(mbedtls_pk_rsa(pk), rsa_padding, MBEDTLS_MD_NONE), 0);
     }
 #else /* MBEDTLS_RSA_C && MBEDTLS_GENPRIME */