Add documentation for the new attributes:
- "bios_active_image"; "bios_auth_fail"; "bios_upgrade_fail";
  "bios_safe_mode" to represent various BIOS statuses.
- "lc{n}_enable" - for put/release the line card to/from enable state.
- "lc{n}_pwr" - for power on/off the line card.
- "lc{n}_rst_mask" - for line card reset state enforced by ASIC, when
  it sets it due to some abnormal ASIC behavior.
- "psu3_on"; "psu4_on" - for connection/disconnection power supply unit
  to/from the power source.
- "pm_mgmt_en" - for setting power management control ownership. When
  power management control is provided by hardware, it means that
  hardware will automatically power off one or more line cards in case
  system power budget is under power required for feeding all powered
  on line cards. It could be a case, when some of power units lost
  power good state.
- "shutdown_unlock" - for unlocking system after hardware or firmware
  thermal shutdown, which causes locking of the all interfaces to ASIC.
Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: Michael Shych <michaelsh@nvidia.com>
Link: https://lore.kernel.org/r/20211002093238.3771419-9-vadimp@nvidia.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>