Revert "regmap: allow to define reg_update_bits for no bus configuration"

This reverts commit 915848be which is
commit 02d6fdec upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I12ce0462c866327af31aead8e35c6b8b413d22d1
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>