tracing: Update MAINTAINERS file for new patchwork and mailing list

The tracing subsystem now has its own mailing list (although patches
should also be sent to LKML) as well as a new patchwork entry for kernel
related tracing patches.

Update the MAINTAINERS file to reflect the changes.

Link: https://lore.kernel.org/linux-trace-kernel/20221017140513.14b9ce2e@gandalf.local.home



Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>