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

This largely reverts commit 5a7b95fb. 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: 5a7b95fb

 ("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+