If user_event_trace_register() fails within user_event_parse() the
call's print_fmt member is not freed. Add kfree call to fix this.

Link: https://lkml.kernel.org/r/20221123183248.554-1-beaub@linux.microsoft.com

Fixes: aa3b2b4c ("user_events: Add print_fmt generation support for basic types")
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>