mm/memcontrol.c: fix kerneldoc comment for mem_cgroup_calculate_protection

make W=1 generates the following warning for mem_cgroup_calculate_protection

  mm/memcontrol.c:6468: warning: expecting prototype for mem_cgroup_protected(). Prototype was for mem_cgroup_calculate_protection() instead

Commit 45c7f7e1 ("mm, memcg: decouple e{low,min} state mutations from
protection checks") changed the function definition but not the associated
kerneldoc comment.

Link: https://lkml.kernel.org/r/20210520084809.8576-7-mgorman@techsingularity.net
Fixes: 45c7f7e1

 ("mm, memcg: decouple e{low,min} state mutations from protection checks")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>