mm/memcontrol.c: remove the useless parameter for mc_handle_swap_pte

mm/memcontrol.c: remove the useless parameter for mc_handle_swap_pte

It seems like this parameter has never been used since being introduced
by 90254a65833b ("memcg: clean up move charge").  Not a big deal because
I assume the function would get inlined into the caller anyway but why
not get rid of it.

[[email protected]: wrote changelog]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Li RongQing <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>