IB/hfi1: Assign npages earlier

Improve code clarity and enable earlier use of
tidbuf->npages by moving its assignment to
structure creation time.

Signed-off-by: Dean Luick <dean.luick@cornelisnetworks.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Link: https://lore.kernel.org/r/167329104884.1472990.4639750192433251493.stgit@awfm-02.cornelisnetworks.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>