ccr,ccp: Fix argument order to sglist_append_vmpages.

The offset comes before the byte count.

Reported by: br
Reviewed by: asomers, markj
MFC after: 1 week
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D38375

(cherry picked from commit 70efe1a2fe13642732e56c7f040fe63f62bc6a6b)