We use raw memory primitives along the !parallel_cpus paths in order to
simplify the endianness handling.  Because of that, we did not benefit
from the generic changes to cpu_ldst_user_only_template.h.

The simplest fix is to manipulate helper_retaddr here.
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>