tracing: Clean up the hwlat binding code

[ Upstream commit f447c196fe7a3a92c6396f7628020cb8d564be15 ]

Instead of initializing the affinity of the hwlat kthread in the thread
itself, simply set up the initial affinity at thread creation. This
simplifies the code.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>