tracing: Convert some kmem events to DEFINE_EVENT

Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
 333987   69800   27228  431015   693a7 mm/built-in.o.old
 330030   69800   27228  427058   68432 mm/built-in.o

8 events are converted:

  kmem_alloc: kmalloc, kmem_cache_alloc
  kmem_alloc_node: kmalloc_node, kmem_cache_alloc_node
  kmem_free: kfree, kmem_cache_free
  mm_page: mm_page_alloc_zone_locked, mm_page_pcpu_drain

No change in functionality.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
LKML-Reference: <4B0E286A.2000405@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>