tracefs: Remove unnecessary debug_fs checks.

This is a preparation for debugfs restricted mode.
We don't need debugfs to trace, the removed check stop tracefs to work
if debugfs is not initialised. We instead tries to automount within
debugfs and relay on it's handling. The code path is to create a
backward compatibility from when tracefs was part of debugfs, it is now
standalone and does not need debugfs. When debugfs is in restricted
it is compiled in but not active and return EPERM to clients and
tracefs wont work if it assumes it is active it is compiled in
kernel.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20200716071511.26864-2-peter.enderborg@sony.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/trace/trace.c

@@ -8945,9 +8945,7 @@ struct dentry *tracing_init_dentry(void)
 	if (tr->dir)
 		return NULL;
 
-	if (WARN_ON(!tracefs_initialized()) ||
-		(IS_ENABLED(CONFIG_DEBUG_FS) &&
-		 WARN_ON(!debugfs_initialized())))
+	if (WARN_ON(!tracefs_initialized()))
 		return ERR_PTR(-ENODEV);
 
 	/*