RDMA/qib: Remove all occurrences of BUG_ON()

QIB driver was added in 2010 with many BUG_ON(), most of them were cleaned
out after years of development and usages.

It looks like that it is safe now to remove rest of BUG_ONs.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>