Define always psa_key_id_t as defined in PSA crypto spec

Define always psa_key_id_t as defined in the PSA
Cryptography API specification independently of
whether the MBEDTLS_PSA_CRYPTO_KEY_FILE_ID_ENCODES_OWNER
configuration file is set or not.

As a consequence, get rid of `psa_app_key_id_t` that is
not needed anymore.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 3600e1a..a9b8624 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -166,7 +166,7 @@
 static int psa_is_key_id_valid( psa_key_file_id_t file_id,
                                 int vendor_ok )
 {
-    psa_app_key_id_t key_id = PSA_KEY_FILE_GET_KEY_ID( file_id );
+    psa_key_id_t key_id = PSA_KEY_FILE_GET_KEY_ID( file_id );
     if( PSA_KEY_ID_USER_MIN <= key_id && key_id <= PSA_KEY_ID_USER_MAX )
         return( 1 );
     else if( vendor_ok &&
@@ -291,14 +291,14 @@
             ++stats->volatile_slots;
         else if( slot->attr.lifetime == PSA_KEY_LIFETIME_PERSISTENT )
         {
-            psa_app_key_id_t id = PSA_KEY_FILE_GET_KEY_ID(slot->attr.id);
+            psa_key_id_t id = PSA_KEY_FILE_GET_KEY_ID(slot->attr.id);
             ++stats->persistent_slots;
             if( id > stats->max_open_internal_key_id )
                 stats->max_open_internal_key_id = id;
         }
         else
         {
-            psa_app_key_id_t id = PSA_KEY_FILE_GET_KEY_ID(slot->attr.id);
+            psa_key_id_t id = PSA_KEY_FILE_GET_KEY_ID(slot->attr.id);
             ++stats->external_slots;
             if( id > stats->max_open_external_key_id )
                 stats->max_open_external_key_id = id;