Change shader cache init wait method (#6131)

* Change shader cache init wait method

* Make field readonly

src/Ryujinx.HLE/HOS/ArmProcessContext.cs

@@ -57,6 +57,8 @@ namespace Ryujinx.HLE.HOS
 
         public void Execute(IExecutionContext context, ulong codeAddress)
         {
+            // We must wait until shader cache is loaded, among other things, before executing CPU code.
+            _gpuContext.WaitUntilGpuReady();
             _cpuContext.Execute(context, codeAddress);
         }