[HLE/Kernel] Fix SetThreadPriority, allow nano seconds values > int.MaxValue, fix on WaitProcessWideKeyAtomic (althrough looks like it still doesn't work properly

Ryujinx.Core/OsHle/Kernel/NsTimeConverter.cs

@@ -0,0 +1,19 @@
+namespace Ryujinx.Core.OsHle.Kernel
+{
+    static class NsTimeConverter
+    {
+        public static int GetTimeMs(ulong Ns)
+        {
+            ulong Ms = Ns / 1_000_000;
+
+            if (Ms < int.MaxValue)
+            {
+                return (int)Ms;
+            }
+            else
+            {
+                return int.MaxValue;
+            }
+        }
+    }
+}