debugfs: Fix terminology inconsistency of dir name to mount debugfs filesystem.

Many developers use "/debug/" or "/debugfs/" or "/sys/kernel/debug/"
directory name to mount debugfs filesystem for ftrace according to
./Documentation/tracers/ftrace.txt file.

And, three directory names(ex:/debug/, /debugfs/, /sys/kernel/debug/) is
existed in kernel source like ftrace, DRM, Wireless, Documentation,
Network[sky2]files to mount debugfs filesystem.

debugfs means debug filesystem for debugging easy to use by greg kroah
hartman. "/sys/kernel/debug/" name is suitable as directory name
of debugfs filesystem.
- debugfs related reference: http://lwn.net/Articles/334546/

Fix inconsistency of directory name to mount debugfs filesystem.

* From Steven Rostedt
  - find_debugfs() and tracing_files() in this patch.

Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
Acked-by     : Inaky Perez-Gonzalez <inaky@linux.intel.com>
Reviewed-by  : Steven Rostedt <rostedt@goodmis.org>
Reviewed-by  : James Smart <james.smart@emulex.com>
CC: Jiri Kosina <trivial@kernel.org>
CC: David Airlie <airlied@linux.ie>
CC: Peter Osterlund <petero2@telia.com>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
CC: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
CC: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 8905068..387a8de 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -343,7 +343,7 @@
 #if defined(CONFIG_DEBUG_FS)
 	ret = drm_debugfs_init(new_minor, minor_id, drm_debugfs_root);
 	if (ret) {
-		DRM_ERROR("DRM: Failed to initialize /debugfs/dri.\n");
+		DRM_ERROR("DRM: Failed to initialize /sys/kernel/debug/dri.\n");
 		goto err_g2;
 	}
 #endif