Replace some calls to MemCopy with small constant sizes with memcpy

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index f539504a7f2cf6ef7899f9d15bd01ba8e53acabf..bc5a26a75b36d630d4527fd17bb249069505077c 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -1675,7 +1675,7 @@ void Assembler::cfc1(Register rt, FPUControlRegister fs) {
 
 void Assembler::DoubleAsTwoUInt32(double d, uint32_t* lo, uint32_t* hi) {
   uint64_t i;
-  MemCopy(&i, &d, 8);
+  memcpy(&i, &d, 8);
 
   *lo = i & 0xffffffff;
   *hi = i >> 32;