RDMA/efa: Group keep alive received counter with other SW stats

The keep alive received counter is a software stat, keep it grouped with
all other software stats.  Since all stored stats are software stats,
remove the efa_sw_stats struct and use efa_stats instead.

Link: https://lore.kernel.org/r/20200915141449.8428-2-galpress@amazon.com


Reviewed-by: Daniel Kranzdorf <dkkranzd@amazon.com>
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>