MIPS: Remove r6 DCHECKs for NEG.fmt instruction

src/mips64/assembler-mips64.cc

Index: src/mips64/assembler-mips64.cc
diff --git a/src/mips64/assembler-mips64.cc b/src/mips64/assembler-mips64.cc
index 21a243453a4bd89afdcb4b167ed63b2c2f80b59f..319e6b8b061f29e41c0b4068c4f64b976b317525 100644
--- a/src/mips64/assembler-mips64.cc
+++ b/src/mips64/assembler-mips64.cc
@@ -2818,13 +2818,11 @@ void Assembler::mov_s(FPURegister fd, FPURegister fs) {
 
 
 void Assembler::neg_s(FPURegister fd, FPURegister fs) {
-  DCHECK(kArchVariant == kMips64r2);
   GenInstrRegister(COP1, S, f0, fs, fd, NEG_D);
 }
 
 
 void Assembler::neg_d(FPURegister fd, FPURegister fs) {
-  DCHECK(kArchVariant == kMips64r2);
   GenInstrRegister(COP1, D, f0, fs, fd, NEG_D);
 }