RDMA/bnxt_re: Fix stat push into dma buffer on gen p5 devices

Due to recent advances in the firmware for Broadcom's gen p5 series of
adaptors the driver code to report hardware counters has been broken
w.r.t. roce devices.

The new firmware command expects dma length to be specified during stat
dma buffer allocation.

Fixes: 2792b5b9 ("bnxt_en: Update firmware interface spec. to 1.10.0.89.")
Link: https://lore.kernel.org/r/1574317343-23300-3-git-send-email-devesh.sharma@broadcom.com


Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>