cmd/compile: add missing tail calls flag for linux/loong64

Set the value of the variable tailCall to true and prevent
allocating or clobber the linker register.

Change-Id: I4ec19c67056cb99196911aa7c0054be89ab7eb8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/414954
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: David Chase <[email protected]>
Run-TryBot: Wayne Zuo <[email protected]>
Reviewed-by: WANG Xuerui <[email protected]>

Author: abner-chenc

src/cmd/compile/internal/ssa/_gen/LOONG64Ops.go

@@ -270,7 +270,7 @@ func init() {
 
 		// function calls
 		{name: "CALLstatic", argLength: 1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                               // call static function aux.(*obj.LSym).  arg0=mem, auxint=argsize, returns mem
-		{name: "CALLtail", argLength: 1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                                                 // tail call static function aux.(*obj.LSym).  arg0=mem, auxint=argsize, returns mem
+		{name: "CALLtail", argLength: 1, reg: regInfo{clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true, tailCall: true},                                 // tail call static function aux.(*obj.LSym).  arg0=mem, auxint=argsize, returns mem
 		{name: "CALLclosure", argLength: 3, reg: regInfo{inputs: []regMask{gpsp, buildReg("R29"), 0}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true}, // call function via closure.  arg0=codeptr, arg1=closure, arg2=mem, auxint=argsize, returns mem
 		{name: "CALLinter", argLength: 2, reg: regInfo{inputs: []regMask{gp}, clobbers: callerSave}, aux: "CallOff", clobberFlags: true, call: true},                         // call fn by pointer.  arg0=codeptr, arg1=mem, auxint=argsize, returns mem