Refactoring the command queue (rcfw) management code. A new data-structure
is introduced to describe the bar register.  each object which deals with
mmio space should have a descriptor structure. This structure specifically
hold DB register information.  Thus, slow path creq structure now hold a
bar register descriptor.

Further cleanup the rcfw structure to introduce the command queue context
and command response event queue context structures. Rest of the rcfw
related code has been touched to incorporate these three structures.

Link: https://lore.kernel.org/r/1581786665-23705-6-git-send-email-devesh.sharma@broadcom.comSigned-off-by: Naresh Kumar PBS <nareshkumar.pbs@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>