IB/hfi1: Fix comment on default hdr entry size

The comment for the default header queue entry size is incorrect.

Correct the comment and fix the resulting S_IRUGO warning that shows
up in the widened patch context.

Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>