devlink: add flash update command

Add devlink flash update command. Advanced NICs have firmware
stored in flash and often cryptographically secured. Updating
that flash is handled by management firmware. Ethtool has a
flash update command which served us well, however, it has two
shortcomings:
 - it takes rtnl_lock unnecessarily - really flash update has
   nothing to do with networking, so using a networking device
   as a handle is suboptimal, which leads us to the second one:
 - it requires a functioning netdev - in case device enters an
   error state and can't spawn a netdev (e.g. communication
   with the device fails) there is no netdev to use as a handle
   for flashing.

Devlink already has the ability to report the firmware versions,
now with the ability to update the firmware/flash we will be
able to recover devices in bad state.

To enable updates of sub-components of the FW allow passing
component name.  This name should correspond to one of the
versions reported in devlink info.

v1: - replace target id with component name (Jiri).

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>