net: cs89x0: remove ISA bus probing

net: cs89x0: remove ISA bus probing

The cs89x0 driver is really two in one, and they are mutually exclusive:

 - the ISA driver was used on 486-era PCs. It likely has no remaining
   users, like the other ethernet drivers that got removed in
   linux-7.1. The DMA support in here is the last device driver use of
   the deprecated isa_bus_to_virt() interface, all other users are either
   x86 specific or or got converted to the normal dma-mapping interface.
   The driver was maintained by Andrew Morton at the time, based on
   the linux-2.2 vendor driver from Cirrus Logic.

 - the platform_driver instance was used on some embedded Arm boards
   around the same time, such as the EP7211 Development Kit. This
   is the same chip, but uses modern devicetree based probing and no DMA.
   This was added by Alexander Shiyan.

Remove the ISA driver as a cleanup, including all of the outdated
documentation referring to its configuration.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260429145624.2948432-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>