trace: move util/buffer.c trace points into correct file

The trace points for util/buffer.c were mistakenly put
in the io/trace-events file, instead of util/trace-events
in

  commit 892bd32e
  Author: Daniel P. Berrange <berrange@redhat.com>
  Date:   Thu Jun 16 09:39:50 2016 +0100

    trace: split out trace events for io/ directory

    Move all trace-events for files in the io/ directory to
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 1473872624-23285-2-git-send-email-berrange@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

io/trace-events

 # See docs/tracing.txt for syntax documentation.
 
-# io/buffer.c
-buffer_resize(const char *buf, size_t olen, size_t len) "%s: old %zd, new %zd"
-buffer_move_empty(const char *buf, size_t len, const char *from) "%s: %zd bytes from %s"
-buffer_move(const char *buf, size_t len, const char *from) "%s: %zd bytes from %s"
-buffer_free(const char *buf, size_t len) "%s: capacity %zd"
-
 # io/task.c
 qio_task_new(void *task, void *source, void *func, void *opaque) "Task new task=%p source=%p func=%p opaque=%p"
 qio_task_complete(void *task) "Task complete task=%p"

util/trace-events

 # See docs/tracing.txt for syntax documentation.
 
+# util/buffer.c
+buffer_resize(const char *buf, size_t olen, size_t len) "%s: old %zd, new %zd"
+buffer_move_empty(const char *buf, size_t len, const char *from) "%s: %zd bytes from %s"
+buffer_move(const char *buf, size_t len, const char *from) "%s: %zd bytes from %s"
+buffer_free(const char *buf, size_t len) "%s: capacity %zd"
+
 # util/oslib-win32.c
 # util/oslib-posix.c
 qemu_memalign(size_t alignment, size_t size, void *ptr) "alignment %zu size %zu ptr %p"