[Bug target/94135] PPC: subfic instead of neg used for rotate right

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94135

--- Comment #3 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Both subfic and neg are 1-2 if run on the integer units.  neg can run on
more units, but it is always 2 cycles then!  (And the conditions where you
*can* have 1 cycle are not very often satisfied, anyway).