The ice driver reads data from the Shadow RAM portion of the NVM during
initialization, including data used to identify the NVM image and device,
such as the ETRACK ID used to populate devlink dev info fw.bundle.

Currently it is using a fixed offset defined by ICE_CSS_HEADER_LENGTH to
compute the appropriate offset. This worked fine for E810 and E822 devices
which both have CSS header length of 330 words.

Other devices, including both E825-C and E830 devices have different sizes
for their CSS header. The use of a hard coded value results in the driver
reading from the wrong block in the NVM when attempting to access the
Shadow RAM copy. This results in the driver reporting the fw.bundle as 0x0
in both the devlink dev info and ethtool -i output.

The first E830 support was introduced by commit ba20ecb1 ("ice: Hook up
4 E830 devices by adding their IDs") and the first E825-C support was
introducted by commit f64e1894 ("ice: introduce new E825C devices
family")

The NVM actually contains the CSS header length embedded in it. Remove the
hard coded value and replace it with logic to read the length from the NVM
directly. This is more resilient against all existing and future hardware,
vs looking up the expected values from a table. It ensures the driver will
read from the appropriate place when determining the ETRACK ID value used
for populating the fw.bundle_id and for reporting in ethtool -i.

The CSS header length for both the active and inactive flash bank is stored
in the ice_bank_info structure to avoid unnecessary duplicate work when
accessing multiple words of the Shadow RAM. Both banks are read in the
unlikely event that the header length is different for the NVM in the
inactive bank, rather than being different only by the overall device
family.

Fixes: ba20ecb1 ("ice: Hook up 4 E830 devices by adding their IDs")
Co-developed-by: Paul Greenwalt <paul.greenwalt@intel.com>
Signed-off-by: Paul Greenwalt <paul.greenwalt@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20240603-net-2024-05-30-intel-net-fixes-v2-2-e3563aa89b0c@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>