tracing/events: convert block trace points to TRACE_EVENT(), fix !CONFIG_BLOCK

Fix building failures when CONFIG_BLOCK == n.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2F1520.8020003@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>