tracing: Print lazy preemption model

Print lazy preemption model in ftrace header when latency-format=1.

# cat /sys/kernel/debug/sched/preempt
none voluntary full (lazy)

Without patch:
latency: 0 us, #232946/232946, CPU#40 | (M:unknown VP:0, KP:0, SP:0 HP:0 #P:80)
^^^^^^^

With Patch:
latency: 0 us, #1897938/25566788, CPU#16 | (M:lazy VP:0, KP:0, SP:0 HP:0 #P:80)
^^^^

Now that lazy preemption is part of the kernel, make sure the tracing
infrastructure reflects that.

Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Shrikanth Hegde <[e-mail]>
Acked-by: Masami Hiramatsu (Google) <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

kernel/trace/trace.c

···
 		   preempt_model_none()      ? "server" :
 		   preempt_model_voluntary() ? "desktop" :
 		   preempt_model_full()      ? "preempt" :
+		   preempt_model_lazy()	     ? "lazy"    :
 		   preempt_model_rt()        ? "preempt_rt" :
 		   "unknown",
 		   /* These are reserved for later use */