topology: mark a function as __init to save some memory

'topology_sysfs_init()' is only called via 'device_initcall'.
It can be marked as __init to save a few bytes of memory.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20200621081106.881915-1-christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>