qed: implement devlink info request

Here we return existing fw & mfw versions, we also fetch device's
serial number:

~$ sudo ~/iproute2/devlink/devlink  dev info
pci/0000:01:00.1:
  driver qed
  board.serial_number REE1915E44552
  versions:
      running:
        fw.app 8.42.2.0
      stored:
        fw.mgmt 8.52.10.0

MFW and FW are different firmwares on device.
Management is a firmware responsible for link configuration and
various control plane features. Its permanent and resides in NVM.

Running FW (or fastpath FW) is an embedded microprogram implementing
all the packet processing, offloads, etc. This FW is being loaded
on each start by the driver from FW binary blob.

The base device specific structure (qed_dev_info) was not directly
available to the base driver before. Thus, here we create and store
a private copy of this structure in qed_dev root object to
access the data.

Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Alexander Lobakin <alobakin@marvell.com>
Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>