psa: cipher: Remove unused `key_set` operation field

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 22dce5d..3dfee3b 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3408,7 +3408,6 @@
     /* Initialize the operation struct members, except for alg. The alg member
      * is used to indicate to psa_cipher_abort that there are resources to free,
      * so we only set it after resources have been allocated/initialized. */
-    operation->key_set = 0;
     operation->iv_set = 0;
     operation->mbedtls_in_use = 0;
     operation->iv_size = 0;
@@ -3444,12 +3443,7 @@
     }
 
 exit:
-    if( status == PSA_SUCCESS )
-    {
-        /* Update operation flags for both driver and software implementations */
-        operation->key_set = 1;
-    }
-    else
+    if( status != PSA_SUCCESS )
         psa_cipher_abort( operation );
 
     unlock_status = psa_unlock_key_slot( slot );
@@ -3607,7 +3601,6 @@
     psa_driver_wrapper_cipher_abort( operation );
 
     operation->alg = 0;
-    operation->key_set = 0;
     operation->iv_set = 0;
     operation->mbedtls_in_use = 0;
     operation->iv_size = 0;