hyperv/vmbus: Avoid extra copy of page information.

The page information array could contain up to 32 elements (i.e. 512B).
And on network side w/ TSO, 11+ (176B+) elements, i.e. ~44K TSO packet,
in the page information array is quite common.

This saves us some cpu cycles.

Reviewed by: adrian, delphij
Approved by: adrian (mentor)
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D4992