tracing: Remove unused ret assignment in tracing_set_tracer()

tracing: Remove unused ret assignment in tracing_set_tracer()

In tracing_set_tracer(), the assignment 'ret = 0' following the
__tracing_resize_ring_buffer() error check is a dead store. After
this point, all subsequent code paths either return with a constant
value (-EINVAL, 0, -EBUSY) or reassign ret before reading it
(tracing_arm_snapshot_locked, tracer_init).

Remove the unnecessary assignment.

No functional change.

Link: https://patch.msgid.link/6a2a37c4.f0a9eb5a.2fc603.7724@mx.google.com
Signed-off-by: Wayen.Yan <win847@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>