mlxsw: minimal: fix potential memory leak in mlxsw_m_linecards_init

In the Linux kernel, the following vulnerability has been resolved:

mlxsw: minimal: fix potential memory leak in mlxsw_m_linecards_init

The line cards array is not freed in the error path of

mlxsw_m_linecards_init(), which can lead to a memory leak. Fix by

freeing the array in the error path, thereby making the error path

identical to mlxsw_m_linecards_fini().