gpiolib: fence off legacy interfaces

gpiolib: fence off legacy interfaces

Merge series from Arnd Bergmann <arnd@kernel.org>:

Commit 678bae2eaa81 ("gpiolib: make legacy interfaces optional") was
merged for linux-6.17, so now it is possible to use the legacy interfaces
conditionally and eventually have the support left out of the kernel
whenever it is not needed.

I created six patches to force-enable CONFIG_GPIOLIB_LEGACY on the
few (mostly ancient) platforms that still require this, plus a set of
patches to either add the corresponding Kconfig dependencies that make
the device drivers conditional on that symbol, or change them to no
longer require it.

The final patch ends up turning the Kconfig symbol off by default,
which of course depends on everything else getting merged first to avoid
build errors.

I would suggest that patches 1-20 can just get merged through the
respective maintainer trees independently when they are deemed ready,
and the final patch can wait another merge window.