cmd/ssadump: fix usage message
cmd/ssadump: fix usage message

Change-Id: I95fee5042e39156462a5c21ade29d7216474be02
Reviewed-on: https://go-review.googlesource.com/8384
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

dmitris/tools,runcom/tools,cw2018/tools,magiccao/tools,springning/tools,runcom/tools,matryer/tools,glasser/golang-tools,nicot/tools,josharian/tools,nicot/tools,cmars/tools,syreclabs/go-tools,golang/tools,argandas/tools,cmars/tools,cw2018/tools,magiccao/tools,matryer/tools,cmars/tools,syreclabs/go-tools,syreclabs/go-tools,runcom/tools,glasser/golang-tools,runcom/tools,springning/tools,golang/tools,dmitris/tools,magiccao/tools,cw2018/tools,sshetty10/tools,syreclabs/go-tools,jdhenke/tools,josharian/tools,jdhenke/tools,matryer/tools,sshetty10/tools,glasser/golang-tools,springning/tools,dmitris/tools,nicot/tools,syreclabs/go-tools,cmars/tools,magiccao/tools,jdhenke/tools,matryer/tools,golang/tools,sshetty10/tools,jdhenke/tools,glasser/golang-tools,josharian/tools,golang/tools,cw2018/tools,sshetty10/tools,argandas/tools,josharian/tools,syreclabs/go-tools,nicot/tools,dmitris/tools,golang/tools,argandas/tools,argandas/tools,springning/tools