linuxlist: Remove casting of ptr from container_of macro

The cast is not present in the original macro and was added
in OpenBSC with commit (be68f6fc6cde1367a4481d2e774a64e2cd657267)
to help using the header with C++. Due the recent issue in
the bssgp flow control code, let's remove the cast to see
wrong pointer usage. In case C++ code doesn't compile anymore
we can see how to add a cast back to it.

Change was proposed by Michael McTernan
1 file changed