The IXP4xx Kconfig we ended up with for mach-ixp4xx creates
as kismet warning:

   WARNING: unmet direct dependencies detected for GPIO_IXP4XX
     Depends on [n]: GPIOLIB [=y] && HAS_IOMEM [=y] && ARCH_IXP4XX [=y] && OF [=n]
     Selected by [y]:
     - ARCH_IXP4XX [=y] && <choice>

This is because it is possible to select ARCH_IXP4XX witout
OF while that selects the GPIO driver that now depends on
OF.

Fix this by creating a single ARCH_IXP4XX kconfig that selects
USE_OF.

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Imre Kaloz <[email protected]>
Cc: Krzysztof Halasa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

'
Signed-off-by: Arnd Bergmann <[email protected]>