misc: keba: Support EEPROM sections as separate devices

The main EEPROM of KEBA CP500 devices is divided into two sections. One
section for type label data like device name, order number, serial
number and so on. The second section is reserved for arbitrary data
stored by the user.

The two sections have a defined range. The first 3 kB for the type label
and the remaining 1 kB for user data. The type label is written during
production and can fill up the whole 3 kB. Thus, the range is fixed and
cannot be changed dynamically.

The two sections cannot be presented as NVMEM cells. A NVMEM cell is
always read and written at once, because the data presented to the user
can differ from the data stored in the physical NVMEM cell. Thus, NVMEM
cells would lead to reading 3 kB for every type label access, even if
only the device name is read. So performance would suffer. But it is
also an indication that NVMEM cells are designed for small data cells
within NVMEM devices.

Register separate NVMEM devices for every section. This enables safe
access to every section. Also different access rights are then possible.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Link: https://lore.kernel.org/r/20241011191257.19702-6-gerhard@engleder-embedded.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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