memcg: get rid of swapaccount leftovers

The swapaccount kernel parameter without any values has been removed by
commit a2c8990aed5a ("memsw: remove noswapaccount kernel parameter") but
it seems that we didn't get rid of all the left overs.

Make sure that menuconfig help text and kernel-parameters.txt are clear
about value for the paramter and remove the stalled comment which is not
very much useful on its own.

Signed-off-by: Michal Hocko <[e-mail]>
Reported-by: Gergely Risko <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/kernel-parameters.txt

···
 			improve throughput, but will also increase the
 			amount of memory reserved for use by the client.
 
-	swapaccount[=0|1]
+	swapaccount=[0|1]
 			[KNL] Enable accounting of swap in memory resource
 			controller if no parameter or 1 is given or disable
 			it if 0 is given (See Documentation/cgroups/memory.txt)

init/Kconfig

···
 	  Memory Resource Controller Swap Extension comes with its price in
 	  a bigger memory consumption. General purpose distribution kernels
 	  which want to enable the feature but keep it disabled by default
-	  and let the user enable it by swapaccount boot command line
+	  and let the user enable it by swapaccount=1 boot command line
 	  parameter should have this option unselected.
 	  For those who want to have the feature enabled by default should
 	  select this option (if, for some reason, they need to disable it

mm/memcontrol.c

···
 #ifdef CONFIG_MEMCG_SWAP
 static int __init enable_swap_account(char *s)
 {
-	/* consider enabled if no parameter or 1 is given */
 	if (!strcmp(s, "1"))
 		really_do_swap_account = 1;
 	else if (!strcmp(s, "0"))