tracing: Clean up after filter logic rewriting

tracing: Clean up after filter logic rewriting

The functions event_{set,clear,}_no_set_filter_flag were only used in
replace_system_preds() [now, renamed to process_system_preds()].

Commit 80765597bc58 ("tracing: Rewrite filter logic to be simpler and
faster") removed the use of those functions in replace_system_preds().

Since then, the functions event_{set,clear,}_no_set_filter_flag were
unused. Fortunately, make CC=clang W=1 indicates this with
-Wunused-function warnings on those three functions.

So, clean up these obsolete unused functions.

Link: https://lkml.kernel.org/r/20201115155336.20248-1-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>