[input_common/joycon] Enumerate SDL devices iff SDL signals change (#4486)

As per SDL documentation this is the "desired" loop.

> Enumerating the HID devices is an expensive operation, so you can call this to see if there have been any system device changes since the last call to this function. A change in the counter returned doesn't necessarily mean that anything has changed, but you can call SDL_hid_enumerate() to get an updated device list.

https://wiki.libsdl.org/SDL3/SDL_hid_device_change_count

Signed-off-by: lizzie <lizzie@eden-emu.dev>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4486
Reviewed-by: Maufeat <sahyno1996@gmail.com>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

src/input_common/drivers/joycon.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
@@ -83,20 +83,21 @@ void Joycons::ScanThread(std::stop_token stop_token) {
     constexpr u16 nintendo_vendor_id = 0x057e;
     Common::SetCurrentThreadName("JoyconScanThread");
 
+    auto last_ret = 0u;
     do {
-        SDL_hid_device_info* devs = SDL_hid_enumerate(nintendo_vendor_id, 0x0);
-        SDL_hid_device_info* cur_dev = devs;
-
-        while (cur_dev) {
-            if (IsDeviceNew(cur_dev)) {
-                LOG_DEBUG(Input, "Device Found,type : {:04X} {:04X}", cur_dev->vendor_id,
-                          cur_dev->product_id);
-                RegisterNewDevice(cur_dev);
+        auto ret = SDL_hid_device_change_count();
+        if (last_ret == 0u || last_ret != ret) {
+            last_ret = ret;
+            SDL_hid_device_info* devs = SDL_hid_enumerate(nintendo_vendor_id, 0x0);
+            for (auto* cur_dev = devs; cur_dev; cur_dev = cur_dev->next) {
+                if (IsDeviceNew(cur_dev)) {
+                    LOG_DEBUG(Input, "Device Found,type : {:04X} {:04X}", cur_dev->vendor_id, cur_dev->product_id);
+                    RegisterNewDevice(cur_dev);
+                }
+                cur_dev = cur_dev->next;
             }
-            cur_dev = cur_dev->next;
+            SDL_hid_free_enumeration(devs);
         }
-
-        SDL_hid_free_enumeration(devs);
     } while (Common::StoppableTimedWait(stop_token, std::chrono::seconds{5}));
 }