[clang][NFC] Replace ARM_STREAMING_ATTR in tests with SME streaming attribute

Some tests were testing SME builtins before the streaming attributes
existed, and so either inserted them or not depending on a macro
definition. The intention was for the macro to be defined once the
attributes were added to clang, but it never was defined. This change
removes the macro logic and adds the attribute now that they have been
added to clang.