Change sizeof to variable rather than struct

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 664b8ae..415dab8 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3822,7 +3822,7 @@
 
     status = psa_driver_wrapper_aead_abort( operation );
 
-    memset( operation, 0, sizeof( psa_aead_operation_t ) );
+    memset( operation, 0, sizeof( *operation ) );
 
     return( status );
 }