tools/mm/slabinfo: fix total_objects attribute name

tools/mm/slabinfo: fix total_objects attribute name

SLUB exports the total_objects sysfs attribute, but slabinfo tries to read
objects_total. As a result, the lookup fails and the field remains zero.

Use the correct attribute name and rename the corresponding structure
member to match.

Fixes: 205ab99dd103 ("slub: Update statistics handling for variable order slabs")
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Link: https://patch.msgid.link/96556748872BB47E+20260612071359.649946-1-chenyichong@uniontech.com
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>