Add break for default cases

Visual Studio has an option to search all files in a solution, so I
did a search in there for "default:" looking for any missing break
statements.

I've left out default statements that return something, and that throw
something, even if via ThrowInvalidType. UNREACHABLE leads towards throw

R_THROW macro leads towards a return

src/core/hle/service/nvdrv/devices/nvhost_ctrl_gpu.cpp

@@ -300,11 +300,10 @@ Kernel::KEvent* nvhost_ctrl_gpu::QueryEvent(u32 event_id) {
         return error_notifier_event;
     case 2:
         return unknown_event;
-    default: {
+    default:
         LOG_CRITICAL(Service_NVDRV, "Unknown Ctrl GPU Event {}", event_id);
+        return nullptr;
     }
-    }
-    return nullptr;
 }
 
 } // namespace Service::Nvidia::Devices

src/core/hle/service/nvdrv/devices/nvhost_gpu.cpp

@@ -364,11 +364,10 @@ Kernel::KEvent* nvhost_gpu::QueryEvent(u32 event_id) {
         return sm_exception_breakpoint_pause_report_event;
     case 3:
         return error_notifier_event;
-    default: {
+    default:
         LOG_CRITICAL(Service_NVDRV, "Unknown Ctrl GPU Event {}", event_id);
+        return nullptr;
     }
-    }
-    return nullptr;
 }
 
 } // namespace Service::Nvidia::Devices