RDMA/qib: Tidy up process_cc()

This function has a lot of gotos which could be replaced by simple
returns, making the function tidier and less bug prone.

Link: https://lore.kernel.org/r/20200825171242.448447-2-alex.dewar90@gmail.com
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>