[loong64][mips] Remove a useless declaration of Operand

Change-Id: Ib4039ede294fe3c108cd49c45a7a5e36a6f51780
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3653714Reviewed-by: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Auto-Submit: Yu Liu <liuyu@loongson.cn>
Cr-Commit-Position: refs/heads/main@{#80640}

src/codegen/loong64/assembler-loong64.h

@@ -41,7 +41,6 @@ class Operand {
       : rm_(no_reg), rmode_(RelocInfo::EXTERNAL_REFERENCE) {
     value_.immediate = static_cast<int64_t>(f.address());
   }
-  V8_INLINE explicit Operand(const char* s);
   explicit Operand(Handle<HeapObject> handle);
   V8_INLINE explicit Operand(Smi value)
       : rm_(no_reg), rmode_(RelocInfo::NO_INFO) {

src/codegen/mips/assembler-mips.h

@@ -71,7 +71,6 @@ class Operand {
       : rm_(no_reg), rmode_(RelocInfo::EXTERNAL_REFERENCE) {
     value_.immediate = static_cast<int32_t>(f.address());
   }
-  V8_INLINE explicit Operand(const char* s);
   explicit Operand(Handle<HeapObject> handle);
   V8_INLINE explicit Operand(Smi value)
       : rm_(no_reg), rmode_(RelocInfo::NO_INFO) {