tracing/selftests: Turn off timeout setting

As the ftrace selftests can run for a long period of time, disable the
timeout that the general selftests have. If a selftest hangs, then it
probably means the machine will hang too.

Link: https://lore.kernel.org/r/alpine.LSU.2.21.1911131604170.18679@pobox.suse.cz

Suggested-by: Miroslav Benes <mbenes@suse.cz>
Tested-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>