sctp: fix some copy-paste errors for file comments

This patch is to fix the file comments in stream.c and
stream_interleave.c

v1->v2:
  rephrase the comment for stream.c according to Neil's suggestion.

Fixes: a8386317 ("sctp: prepare asoc stream for stream reconf")
Fixes: 0c3f6f65 ("sctp: implement make_datafrag for sctp_stream_interleave")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>