mm: kmemleak: split __create_object into two functions

__create_object() consists of two part, the first part allocate a kmemleak
object and initialize it, the second part insert it into object tree. 
This function need kmemleak_lock but actually only the second part need
lock.

Split it into two functions, the first function __alloc_object only
allocate a kmemleak object, and the second function __link_object() will
initialize the object and insert it into object tree, use the
kmemleak_lock to protect __link_object() only.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20231018102952.3339837-5-liushixin2@huawei.com


Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Patrick Wang <patrick.wang.shcn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>