fix rak4631 builds after addition of xio nrf52 board

Author: liamcottle

variants/rak4631/platformio.ini

@@ -16,7 +16,7 @@ build_flags = ${nrf52840_base.build_flags}
   -D SX126X_CURRENT_LIMIT=130
   -D SX126X_RX_BOOSTED_GAIN=1
 build_src_filter = ${nrf52840_base.build_src_filter}
-  +<helpers/nrf52/*.cpp>
+  +<helpers/nrf52/RAK4631Board.cpp>
   +<../variants/rak4631>
 lib_deps =
   ${nrf52840_base.lib_deps}
@@ -86,7 +86,7 @@ build_flags =
 ;  -D MESH_DEBUG=1
 build_src_filter = ${rak4631.build_src_filter}
   +<helpers/ui/*.cpp>
-  +<helpers/nrf52/*.cpp>
+  +<helpers/nrf52/SerialBLEInterface.cpp>
   +<../examples/companion_radio>
 lib_deps =
   ${rak4631.lib_deps}