IB/hfi1: List all receive contexts from debugfs

The current debugfs output for receive contexts (rcds), stops after the
kernel receive contexts have been displayed.  This is not enough
information to fully diagnose packet drops.

Display all of the receive contexts.

Augment the output with some more context information.

Limit the ring buffer header output to 5 entries to avoid overextending
the sequential file output.

Fixes: bf808b50

 ("IB/hfi1: Add kernel receive context info to debugfs")
Link: https://lore.kernel.org/r/20191219211928.58387.20737.stgit@awfm-01.aw.intel.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>