tracing: incorrect isolate_mote_t cast in mm_vmscan_lru_isolate

tracing: incorrect isolate_mote_t cast in mm_vmscan_lru_isolate

Fixes following sparse warnings:

  CHECK   mm/vmscan.c
mm/vmscan.c: note: in included file (through
include/trace/trace_events.h, include/trace/define_trace.h,
include/trace/events/vmscan.h):
./include/trace/events/vmscan.h:281:1: sparse: warning:
 cast to restricted isolate_mode_t
./include/trace/events/vmscan.h:281:1: sparse: warning:
 restricted isolate_mode_t degrades to integer

Link: https://lkml.kernel.org/r/e85d7ff2-fd10-53f8-c24e-ba0458439c1b@openvz.org
Signed-off-by: Vasily Averin <vvs@openvz.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>