IB/hfi1: Fix math bugs in hfi1_can_pin_pages()

Fix arithmetic and logic errors in hfi1_can_pin_pages() that  would allow
hfi1 to attempt pinning pages in cases where it should not because of
resource limits or lack of required capability.

Fixes: 2c97ce4f ("IB/hfi1: Add pin query function")
Link: https://lore.kernel.org/r/167656658362.2223096.10954762619837718026.stgit@awfm-02.cornelisnetworks.com


Signed-off-by: Brendan Cunningham <bcunningham@cornelisnetworks.com>
Signed-off-by: Patrick Kelsey <pat.kelsey@cornelisnetworks.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>