tracefs: Rename and export some tracefs functions

Export a few tracefs functions that will be needed by the eventfs dynamic
file system. Rename them to start with "tracefs_" to keep with the name
space.

start_creating -> tracefs_start_creating
failed_creating -> tracefs_failed_creating
end_creating -> tracefs_end_creating

Link: https://lkml.kernel.org/r/1690568452-46553-4-git-send-email-akaher@vmware.com

Signed-off-by: Ajay Kaher <akaher@vmware.com>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: Ching-lin Yu <chinglinyu@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>