Skip the standalone nodes, when gpu_metrics is present

Currently we open the standalone busy, temp, gpu/memory clock and
power_usage nodes, even if gpu_metrics is present.

At the same time, we correctly ignore them when doing the read-only.
So just avoid opening them all together.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

src/gpu.h

@@ -7,10 +7,11 @@
 
 struct amdgpu_files
 {
-    FILE *busy;
-    FILE *temp;
     FILE *vram_total;
     FILE *vram_used;
+    /* The following can be NULL, in that case we're using the gpu_metrics node */
+    FILE *busy;
+    FILE *temp;
     FILE *core_clock;
     FILE *memory_clock;
     FILE *power_usage;

src/overlay.cpp

@@ -639,13 +639,16 @@ void init_gpu_stats(uint32_t& vendorID, uint32_t reported_deviceID, overlay_para
             SPDLOG_DEBUG("Using gpu_metrics");
          }
          path += "/device";
-         if (!amdgpu.busy)
-            amdgpu.busy = fopen((path + "/gpu_busy_percent").c_str(), "r");
          if (!amdgpu.vram_total)
             amdgpu.vram_total = fopen((path + "/mem_info_vram_total").c_str(), "r");
          if (!amdgpu.vram_used)
             amdgpu.vram_used = fopen((path + "/mem_info_vram_used").c_str(), "r");
 
+         if (!metrics_path.empty())
+            break;
+
+         if (!amdgpu.busy)
+            amdgpu.busy = fopen((path + "/gpu_busy_percent").c_str(), "r");
          path += "/hwmon/";
          auto dirs = ls(path.c_str(), "hwmon", LS_DIRS);
          for (auto& dir : dirs) {