mm tracing: tell mm_migrate_pages event about numa_misplaced

The mm_migrate_pages trace event reports a reason for the migration,
typically as a symbolic string.  The exception is the reason
MR_NUMA_MISPLACED for which it just displays the numeric value:
mm_migrate_pages: nr_succeeded=1 nr_failed=0 mode=MIGRATE_ASYNC
reason=0x5

This patch makes the output consistent by introducing a string value for
MR_NUMA_MISPLACED.  The event is then reported as: mm_migrate_pages:
nr_succeeded=1 nr_failed=0 mode=MIGRATE_ASYNC reason=numa_misplaced
Signed-off-by: Max Asbock <masbock@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/trace/events/migrate.h

@@ -17,6 +17,7 @@
 	{MR_MEMORY_HOTPLUG,	"memory_hotplug"},		\
 	{MR_SYSCALL,		"syscall_or_cpuset"},		\
 	{MR_MEMPOLICY_MBIND,	"mempolicy_mbind"},		\
+	{MR_NUMA_MISPLACED,	"numa_misplaced"},		\
 	{MR_CMA,		"cma"}
 
 TRACE_EVENT(mm_migrate_pages,