Merge branch 'implement-dev-info-and-dev-flash-for-line-cards'

Jiri Pirko says:

====================
Implement dev info and dev flash for line cards

This patchset implements two features:
1) "devlink dev info" is exposed for line card (patches 6-9)
2) "devlink dev flash" is implemented for line card gearbox
   flashing (patch 10)

For every line card, "a nested" auxiliary device is created which
allows to bind the features mentioned above (patch 4).

The relationship between line card and its auxiliary dev devlink
is carried over extra line card netlink attribute (patches 3 and 5).

The first patch removes devlink_mutex from devlink_register/unregister()
which eliminates possible deadlock during devlink reload command. The
second patchset follows up with putting net pointer check into new
helper.

Examples:

$ devlink lc show pci/0000:01:00.0 lc 1
pci/0000:01:00.0:
  lc 1 state active type 16x100G nested_devlink auxiliary/mlxsw_core.lc.0
    supported_types:
       16x100G

$ devlink dev show auxiliary/mlxsw_core.lc.0
auxiliary/mlxsw_core.lc.0

$ devlink dev info auxiliary/mlxsw_core.lc.0
auxiliary/mlxsw_core.lc.0:
  versions:
      fixed:
        hw.revision 0
        fw.psid MT_0000000749
      running:
        ini.version 4
        fw 19.2010.1312

$ devlink dev flash auxiliary/mlxsw_core.lc.0 file mellanox/fw-AGB-rel-19_2010_1312-022-EVB.mfa2
====================

Link: https://lore.kernel.org/r/20220725082925.366455-1-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>