Revert "i2c: core: support bus regulator controlling in adapter"

Revert "i2c: core: support bus regulator controlling in adapter"

This largely reverts commit e73669244f65eb63686d89331136470fd8df1c7b. It
breaks suspend with AMD GPUs, and we couldn't incrementally fix it. So,
let's remove the code and go back to the drawing board. We keep the
header extension to not break drivers already populating the regulator.
We expect to re-add the code handling it soon.

Fixes: e73669244f65 ("i2c: core: support bus regulator controlling in adapter")
Reported-by: "Tareque Md.Hanif" <tarequemd.hanif@yahoo.com>
Link: https://lore.kernel.org/r/1295184560.182511.1639075777725@mail.yahoo.com
Reported-by: Konstantin Kharlamov <hi-angel@yandex.ru>
Link: https://lore.kernel.org/r/7143a7147978f4104171072d9f5225d2ce355ec1.camel@yandex.ru
BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1850
Tested-by: "Tareque Md.Hanif" <tarequemd.hanif@yahoo.com>
Tested-by: Konstantin Kharlamov <hi-angel@yandex.ru>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Cc: <stable@vger.kernel.org> # 5.14+