remove useless const_cast

Change-Id: Ia079611d8d9486d558a85f73bfbb95d0b75c0a93
diff --git a/cmsg.cpp b/cmsg.cpp
index 95db303..5a137c3 100644
--- a/cmsg.cpp
+++ b/cmsg.cpp
@@ -83,7 +83,7 @@
   }
 
   alignas(struct cmsghdr) char cmsg_buf[cmsg_space];
-  iovec iov = {.iov_base = const_cast<void*>(data), .iov_len = len};
+  iovec iov = {.iov_base = data, .iov_len = len};
   msghdr msg = {
       .msg_name = nullptr,
       .msg_namelen = 0,