tracing: Have tracing_snapshot_instance_cond() write errors to the appropriate instance

tracing: Have tracing_snapshot_instance_cond() write errors to the appropriate instance

If a trace instance has a failure with its snapshot code, the error
message is to be written to that instance's buffer. But currently, the
message is written to the top level buffer. Worse yet, it may also disable
the top level buffer and not the instance that had the issue.

Link: https://lkml.kernel.org/r/[email protected]
Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Ross Zwisler <[email protected]>
Fixes: 2824f50332486 ("tracing: Make the snapshot trigger work with instances")
Signed-off-by: Steven Rostedt (Google) <[email protected]>