cdvdgigaherz: Avoid holding lock during thread sleep

Fixes Coverity CID 127721: Program hangs

Change the sleep to a condition variable wait, which has the added
benefit of allowing the plugin to close ever so slightly faster if
there's no disc in the drive.

plugins/cdvdGigaherz/src/ReadThread.cpp

@@ -176,7 +176,7 @@ void cdvdThread()
     while (cdvd_is_open) {
         if (cdvdUpdateDiscStatus()) {
             // Need to sleep some to avoid an aggressive spin that sucks the cpu dry.
-            std::this_thread::sleep_for(std::chrono::milliseconds(10));
+            s_notify_cv.wait_for(guard, std::chrono::milliseconds(10));
             continue;
         }