[PATCH V4 0/1] livepatch: Add "stack_order" sysfs attribute

[Wardenjohn <zhangwarden@gmail.com>]

As previous discussion, maintainers think that patch-level sysfs interface is the
only acceptable way to maintain the information of the order that klp_patch is 
applied to the system.

However, the previous patch introduce klp_ops into klp_func is a optimization 
methods of the patch introducing 'using' feature to klp_func.

But now, we don't support 'using' feature to klp_func and make 'klp_ops' patch
not necessary.

Therefore, this new version is only introduce the sysfs feature of klp_patch 
'stack_order'.

V1 -> V2:
1. According to the suggestion from Petr, to make the meaning more clear, rename
'order' to 'stack_order'.
2. According to the suggestion from Petr and Miroslav, this patch now move the 
calculating process to stack_order_show function. Adding klp_mutex lock protection.

V2 -> V3:
1. Squash 2 patches into 1. Update description of stack_order in ABI Document.
(Suggested by Miroslav)
2. Update subject and commit log. (Suggested by Miroslav)
3. Update code format for some line of the patch. (Suggested by Miroslav)

V3 -> V4:
1. Rebase the patch of to branch linux-master.
2. Update the description of ABI Document Description. (Suggested by Petr & Josh)

Regards.
Wardenjohn.