slab: convert setup_slub_debug() to use __core_param_cb()

slab: convert setup_slub_debug() to use __core_param_cb()

Use __core_param_cb() to parse the "slab_debug" kernel parameter instead of
the obsolescent __setup(). For now, the parameter is not exposed in sysfs,
and no get ops is provided.

There is a slight change in behavior. Before this patch, the following
parameter would silently turn on full debugging for all slabs:

  slub_debug_yada_yada_gotta_love_this=hail_satan!

This syntax is now rejected, and the parameter will be passed to user
space, making the kernel a holier place.

Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Link: https://patch.msgid.link/9674b34861394088c7853edf8e9d2b439fd4b42f.1761324765.git.ptesarik@suse.com
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>