RDMA/bnxt_re: Add 64bit doorbells for 57500 series

RDMA/bnxt_re: Add 64bit doorbells for 57500 series

The new chip series has 64 bit doorbell for notification queues. Thus,
both control and data path event queues need new routines to write 64 bit
doorbell. Adding the same. There is new doorbell interface between the
chip and driver. Changing the chip specific data structure definitions.

Additional significant changes are listed below
- bnxt_re_net_ring_free/alloc takes a new argument
- bnxt_qplib_enable_nq and enable_rcfw uses new doorbell offset
  for new chip.
- DB mapping for NQ and CREQ now maps 8 bytes.
- DBR_DBR_* macros renames to DBC_DBC_*
- store nq_db_offset in a 32bit data type.
- got rid of __iowrite64_copy, used writeq instead.
- changed the DB header initialization to simpler scheme.

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>