target/ppc: use TCG_CALL_NO_RWG in VSX helpers without env

Helpers of VSX instructions without cpu_env as an argument do not access
globals.

Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220517123929.284511-5-matheus.ferst@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>