Revert the accidental cast change in codegen-x64 for the trunk push.

git-svn-id: http://v8.googlecode.com/svn/trunk@2804 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index c61cdc9..f75854a 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -6377,7 +6377,7 @@
         // One operand is a smi.
 
         // Check whether the non-smi is a heap number.
-        ASSERT_EQ(static_cast<intptr_t>(1), kSmiTagMask);
+        ASSERT_EQ(1, kSmiTagMask);
         // rcx still holds rax & kSmiTag, which is either zero or one.
         __ decq(rcx);  // If rax is a smi, all 1s, else all 0s.
         __ movq(rbx, rdx);