Use PS4 rumble hint as the default for the PS5 rumble hint

Existing SDL applications may not know about the need to set a specific
hint to enable rumble on PS5 controllers, even though they may already
set the equivalent SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE hint for PS4
controller rumble support.

Rather than requiring those developers update their apps, let's use the
SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE value as an indication of the behavior
they are expected for all PlayStation controllers.

include/SDL_hints.h

@@ -616,6 +616,11 @@ extern "C" {
  *
  *  Once extended reports are enabled, they can not be disabled without
  *  power cycling the controller.
+ *
+ *  For compatibility with applications written for versions of SDL prior
+ *  to the introduction of PS5 controller support, this value will also
+ *  control the state of extended reports on PS5 controllers when the
+ *  SDL_HINT_JOYSTICK_HIDAPI_PS5_RUMBLE hint is not explicitly set.
  */
 #define SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE "SDL_JOYSTICK_HIDAPI_PS4_RUMBLE"
 
@@ -642,6 +647,10 @@ extern "C" {
  *
  *  Once extended reports are enabled, they can not be disabled without
  *  power cycling the controller.
+ *
+ *  For compatibility with applications written for versions of SDL prior
+ *  to the introduction of PS5 controller support, this value defaults to
+ *  the value of SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE.
  */
 #define SDL_HINT_JOYSTICK_HIDAPI_PS5_RUMBLE "SDL_JOYSTICK_HIDAPI_PS5_RUMBLE"
 

src/joystick/hidapi/SDL_hidapi_ps5.c

@@ -624,7 +624,13 @@ HIDAPI_DriverPS5_OpenJoystick(SDL_HIDAPI_Device *device, SDL_Joystick *joystick)
     } else {
         /* Connected over Bluetooth, using simple reports (DirectInput enabled) */
         ctx->is_bluetooth = SDL_TRUE;
-        enhanced_mode = SDL_GetHintBoolean(SDL_HINT_JOYSTICK_HIDAPI_PS5_RUMBLE, SDL_FALSE);
+
+        /* Games written prior the introduction of PS5 controller support in SDL will not be aware of
+           SDL_HINT_JOYSTICK_HIDAPI_PS5_RUMBLE, but they did know SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE.
+           To support apps that only knew about the PS4 hint, we'll use the PS4 hint as the default.
+        */
+        enhanced_mode = SDL_GetHintBoolean(SDL_HINT_JOYSTICK_HIDAPI_PS5_RUMBLE,
+                                           SDL_GetHintBoolean(SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE, SDL_FALSE));
     }
 
     if (enhanced_mode) {