refactor(split): move event listener out of Bluetooth directory

app/src/split/CMakeLists.txt

@@ -1,6 +1,10 @@
 # Copyright (c) 2022 The ZMK Contributors
 # SPDX-License-Identifier: MIT
 
+if (CONFIG_ZMK_SPLIT_BLE AND (NOT CONFIG_ZMK_SPLIT_ROLE_CENTRAL))
+  target_sources(app PRIVATE listener.c)
+endif()
+
 if (CONFIG_ZMK_SPLIT_BLE)
     add_subdirectory(bluetooth)
 endif()

app/src/split/bluetooth/CMakeLists.txt

@@ -2,10 +2,10 @@
 # SPDX-License-Identifier: MIT
 
 if (NOT CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
-  target_sources(app PRIVATE split_listener.c)
   target_sources(app PRIVATE service.c)
   target_sources(app PRIVATE peripheral.c)
 endif()
+
 if (CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
   target_sources(app PRIVATE central.c)
 endif()