mm, memcg: mark cgroup_memory_nosocket, nokmem and noswap as __ro_after_init

cgroup_memory_nosocket, cgroup_memory_nokmem and cgroup_memory_noswap
are initialized during the kernel initialization and never change
their value afterwards.

cgroup_memory_nosocket, cgroup_memory_nokmem are written only from
cgroup_memory(), which is marked as __init.

cgroup_memory_noswap is written from setup_swap_account() and
mem_cgroup_swap_init(), both are marked as __init.

Mark all three variables as __ro_after_init.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>

mm/memcontrol.c

@@ -80,14 +80,14 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
 DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
 
 /* Socket memory accounting disabled? */
-static bool cgroup_memory_nosocket;
+static bool cgroup_memory_nosocket __ro_after_init;
 
 /* Kernel memory accounting disabled? */
-static bool cgroup_memory_nokmem;
+static bool cgroup_memory_nokmem __ro_after_init;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
-bool cgroup_memory_noswap __read_mostly;
+bool cgroup_memory_noswap __ro_after_init;
 #else
 #define cgroup_memory_noswap		1
 #endif