make string variable 'tpath' an empty string.

string variable not being empty can lead to incorrect compilation
and corrupted output.

Change-Id: Ie66756c28aef7417759c29387500970a8b53e44c


[ROCm/rocm_smi_lib commit: dbe3403bd3]

projects/rocm-smi-lib/src/rocm_smi_main.cc

@@ -181,7 +181,7 @@ static bool bdfid_from_path(const std::string in_name, uint64_t *bdfid) {
 
 static uint32_t ConstructBDFID(std::string path, uint64_t *bdfid) {
   assert(bdfid != nullptr);
-  char tpath[256];
+  char tpath[256] = {'\0'};
   ssize_t ret;
   memset(tpath,0,256);