AArch64: Fix unused variable warning breaking bootstrap.

This marks the parameter &fi as unused so it doesn't
cause a boostrap failure.

committed under the obvious rule.

gcc/ChangeLog:

	* config/aarch64/aarch64-sve-builtins-base.cc (memory_vector_mode):
	Mark parameter unused.

gcc/ChangeLog

+2020-01-18  Tamar Christina  <tamar.christina@arm.com>
+
+	* config/aarch64/aarch64-sve-builtins-base.cc (memory_vector_mode):
+	Mark parameter unused.
+
 2020-01-18  Hans-Peter Nilsson  <hp@axis.com>
 
 	* config.gcc <obsolete targets>: Add crisv32-*-* and cris-*-linux*

gcc/config/aarch64/aarch64-sve-builtins-base.cc

@@ -1206,7 +1206,7 @@ class svld1ro_impl : public load_replicate
 {
 public:
   machine_mode
-  memory_vector_mode (const function_instance &fi) const OVERRIDE
+  memory_vector_mode (const function_instance &fi ATTRIBUTE_UNUSED) const OVERRIDE
   {
     return OImode;
   }