Prevent stack buffer overflow

readlink() does not append a null byte to buffer. Initialize the
tpath to prevent stack buffer overflow.

Change-Id: I17895dc3576b080a0c35bd0528a5b83223ec1c1b

src/rocm_smi_main.cc

@@ -183,6 +183,7 @@ static uint32_t ConstructBDFID(std::string path, uint64_t *bdfid) {
   assert(bdfid != nullptr);
   char tpath[256];
   ssize_t ret;
+  memset(tpath,0,256);
 
   ret = readlink(path.c_str(), tpath, 256);