IB/hfi1: Add packet histogram trace event

IB/hfi1: Add packet histogram trace event

Add a simple trace event taking context number and building simple
histogram to print packets distribution between contexts.

Link: https://lore.kernel.org/r/20200511160700.173205.84270.stgit@awfm-01.aw.intel.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Grzegorz Andrejczuk <grzegorz.andrejczuk@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>