[Bug target/86938] Invalid register name for r8w

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86938

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The rNd, rNw, and rNb aliases for rN (r8-r15) are not currently supported as
far as I can tell.  Use r8 instead.