mlxsw: core_linecards: Fix double memory deallocation in case of invalid INI file

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

mlxsw: core_linecards: Fix double memory deallocation in case of invalid INI file

In case of invalid INI file mlxsw_linecard_types_init() deallocates memory

but doesn't reset pointer to NULL and returns 0. In case of any error

occurred after mlxsw_linecard_types_init() call, mlxsw_linecards_init()

calls mlxsw_linecard_types_fini() which performs memory deallocation again.

Add pointer reset to NULL.

Found by Linux Verification Center (linuxtesting.org) with SVACE.