tracefs: Removed unused 'ret' variable in eventfs_iterate()

Moving to guard() usage removed the need of using the 'ret' variable but
it wasn't removed. As it was set to zero, the compiler in use didn't warn
(although some compilers do).

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20260414110344.75c0663f@robin
Fixes: 4d9b262031f ("eventfs: Simplify code using guard()s")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604100111.AAlbQKmK-lkp@intel.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>