tracing: Update btrfs's tracepoints to use u64 interface

To avoid 64->32 truncating WARNING, update btrfs's tracepoints.

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Link: http://lkml.kernel.org/r/4DACE6E3.8080200@cn.fujitsu.com


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>