POWER: fix `TRPPC64CodeGenerator >> #virtualRegistersReadByProcessorI…

…nstruction:do:`

Fix slip in `virtualRegistersReadByProcessorInstruction:do:` where registers in
field named `rs` were simply ignored.

Arguably, current way of determining what registers are read and assigned
by an instruction is stupid. We really should use instruction semantics
and extract this information from there.

src/Tinyrossa-POWER/TRPPC64CodeGenerator.class.st

@@ -81,7 +81,7 @@ TRPPC64CodeGenerator >> virtualRegistersReadBy: instruction do: block [
  ]. 
 
  instruction externalBindings keysAndValuesDo: [ :name :value |
- (#('ra' 'rb' 'rc') includes: name) ifTrue: [ 
+ (#('ra' 'rb' 'rc' 'rs') includes: name) ifTrue: [ 
  (value isBitVector and: [ value isSymbolic and: [ value isConstant ] ]) ifTrue: [ 
  | vReg |