Remove mutex calls in psa_wipe_all_key_slots

Code size and code style improvement, these calls aren't needed.

Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index f4c6ee0..9890de6 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -144,9 +144,6 @@
 {
     size_t slot_idx;
 
-#if defined(MBEDTLS_THREADING_C)
-    mbedtls_mutex_lock(&mbedtls_threading_key_slot_mutex);
-#endif
     for (slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++) {
         psa_key_slot_t *slot = &global_data.key_slots[slot_idx];
         slot->registered_readers = 1;
@@ -154,9 +151,6 @@
         (void) psa_wipe_key_slot(slot);
     }
     global_data.key_slots_initialized = 0;
-#if defined(MBEDTLS_THREADING_C)
-    mbedtls_mutex_unlock(&mbedtls_threading_key_slot_mutex);
-#endif
 }
 
 psa_status_t psa_reserve_free_key_slot(psa_key_id_t *volatile_key_id,