Flag guard virtual cpufreq support

The feature is guarded by the RELEASE_AVF_ENABLE_VIRT_CPUFREQ flag.  In
Virtualization manager, --virt-cpufreq and --host-cpu-topology is only
passed to crosvm when launching a VM if this feature is enabled.

Bug: 322415363
Test: Builds

Change-Id: I35dca05b42323bdca4f5855bbfe991ba90bbb229
Signed-off-by: David Dai <davidai@google.com>
diff --git a/virtualizationmanager/src/crosvm.rs b/virtualizationmanager/src/crosvm.rs
index 4b3478e..fe8a587 100644
--- a/virtualizationmanager/src/crosvm.rs
+++ b/virtualizationmanager/src/crosvm.rs
@@ -810,8 +810,10 @@
     }
 
     if config.host_cpu_topology {
-        // TODO(b/266664564): replace with --host-cpu-topology once available
-        if let Some(cpus) = get_num_cpus() {
+        if cfg!(virt_cpufreq) {
+            command.arg("--host-cpu-topology");
+            command.arg("--virt-cpufreq");
+        } else if let Some(cpus) = get_num_cpus() {
             command.arg("--cpus").arg(cpus.to_string());
         } else {
             bail!("Could not determine the number of CPUs in the system");