hash/crc32: fix comment that the IEEE polynomial applies to MPEG-2.
hash/crc32: fix comment that the IEEE polynomial applies to MPEG-2.

LGTM=minux
R=adg, minux
CC=golang-codereviews
https://codereview.appspot.com/170520043

tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go