Revert "suppress warning on GCC 7 and later"

This reverts commit a630ad73cb.

modules/dnn/CMakeLists.txt

@@ -35,10 +35,6 @@ else()
                                        -Wunused-parameter -Wsign-compare
   )
 endif()
-if(ARM AND CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0)
-  # suppress warnings from GCC only on 7.1 and later
-  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-psabi)
-endif()
 if(HAVE_CUDA)
   ocv_warnings_disable(CMAKE_CXX_FLAGS -Wundef)
 endif()