blktrace: from-sector redundant in trace_block_remap, cleanup

The last argument of block_remap prober is the original sector
before remap, so it should be 'from', not 'to'.

[ Impact: clean up ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: "Alan D. Brunelle" <Alan.Brunelle@hp.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
LKML-Reference: <4A07CE86.5090301@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>