modules: hal_nxp: Fix bt_controller cmake load issue

  - In middleware/CMakeLists.txt, using add_subdirectory()
    to load the cmakelists.txt under bt_controller will
    result in the bt_controller directory not being found
    correctly, because the starting point of the query
    is mcux-sdk-ng/CMakeLists.txt. Need to add
    ${CMAKE_CURRENT_LIST_DIR} to bt_controller to correctly
    locate the folder.

Signed-off-by: Zhaoxiang Jin <Zhaoxiang.Jin_1@nxp.com>