gfxstream: make sure by default descriptor is negative

Otherwise, another valid fd may be closed.

Cc: mesa-stable
Reviewed-by: Aaron Ruby <aruby@qnx.com
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34885>

src/gfxstream/guest/platform/linux/LinuxVirtGpu.h

@@ -73,7 +73,7 @@ class LinuxVirtGpuDevice : public VirtGpuDevice {
     virtual bool getPciBusInfo(VirtGpuPciBusInfo* pciBusInfo) override;
 
    private:
-    int64_t mDeviceHandle;
+    int64_t mDeviceHandle = -1;
     struct VirtGpuCaps mCaps;
 
     int openDevice();