[Bug rtl-optimization/79858] Explain to translators what %smode means

[roland.illig at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79858

--- Comment #2 from Roland Illig <roland.illig at gmx dot de> ---
What about the letters "mode"? Are they to be translated? Or should the
resulting text, even in Arabic, be "QImode"?