am: add IsVrModeEnabled (#1189)

* am: stub IsVrMode

Needed by SSBU 7.0.0

* Address Ac_K's comments

Ryujinx.HLE/HOS/Services/Am/AppletAE/AllSystemAppletProxiesService/SystemAppletProxy/ICommonStateGetter.cs

@@ -9,7 +9,8 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Sys
 {
     class ICommonStateGetter : IpcService
     {
-        private CpuBoostMode _cpuBoostMode = CpuBoostMode.Disabled;
+        private CpuBoostMode _cpuBoostMode  = CpuBoostMode.Disabled;
+        private bool         _vrModeEnabled = false;
 
         public ICommonStateGetter() { }
 
@@ -89,6 +90,15 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletAE.AllSystemAppletProxiesService.Sys
             return ResultCode.Success;
         }
 
+        [Command(50)] // 3.0.0+
+        // IsVrModeEnabled() -> b8
+        public ResultCode IsVrModeEnabled(ServiceCtx context)
+        {
+            context.ResponseData.Write(_vrModeEnabled);
+
+            return ResultCode.Success;
+        }
+
         [Command(60)] // 3.0.0+
         // GetDefaultDisplayResolution() -> (u32, u32)
         public ResultCode GetDefaultDisplayResolution(ServiceCtx context)