Fix env var name for CL_AGENT

This got incorrectly renamed to VDI_AGENT
Change-Id: Ifd7f7c89c0a4e4bfc29e0bceae2c22bf6ba01379

rocclr/platform/agent.cpp

@@ -179,7 +179,7 @@ bool Agent::init() {
   //    potentialCapabilities_.canGenerateProgramEvents      = 1;
   //    potentialCapabilities_.canGenerateKernelEvents       = 1;
 
-  const char* envVar = ::getenv("VDI_AGENT");
+  const char* envVar = ::getenv("CL_AGENT");
   if (envVar == NULL) {
     return true;
   }