Set input cost as 1 for psa_key_exercise test

Signed-off-by: Kusumit Ghoderao <Kusumit.Ghoderao@silabs.com>
diff --git a/tests/src/psa_exercise_key.c b/tests/src/psa_exercise_key.c
index 8335977..c4488b5 100644
--- a/tests/src/psa_exercise_key.c
+++ b/tests/src/psa_exercise_key.c
@@ -438,10 +438,9 @@
                                                   PSA_KEY_DERIVATION_INPUT_LABEL,
                                                   input2, input2_length));
     } else if (PSA_ALG_IS_PBKDF2(alg)) {
-        data_t input_cost = { (unsigned char *) input1, (uint32_t) input1_length };
         PSA_ASSERT(psa_key_derivation_input_integer(operation,
                                                     PSA_KEY_DERIVATION_INPUT_COST,
-                                                    parse_binary_string(&input_cost)));
+                                                    1U));
         PSA_ASSERT(psa_key_derivation_input_bytes(operation,
                                                   PSA_KEY_DERIVATION_INPUT_SALT,
                                                   input2,