Remove unused SourceLoc in many Mach data structures (#4180)

* Remove unused srcloc in MachReloc

* Remove unused srcloc in MachTrap

* Use `into_iter` on array in bench code to suppress a warning

* Remove unused srcloc in MachCallSite

cranelift/codegen/src/isa/x64/inst/mod.rs

@@ -601,9 +601,7 @@ impl Inst {
     }
 
     pub(crate) fn trap(trap_code: TrapCode) -> Inst {
-        Inst::Ud2 {
-            trap_code: trap_code,
-        }
+        Inst::Ud2 { trap_code }
     }
 
     pub(crate) fn setcc(cc: CC, dst: Writable<Reg>) -> Inst {
@@ -2432,10 +2430,6 @@ impl EmitState {
     fn clear_post_insn(&mut self) {
         self.stack_map = None;
     }
-
-    pub(crate) fn cur_srcloc(&self) -> SourceLoc {
-        self.cur_srcloc
-    }
 }
 
 /// A label-use (internal relocation) in generated code.