Revert "nvmem: core: fix registration vs use race"

This reverts commit 2dcb474a which is
commit ab3428cf upstream.

It breaks the Android kernel api, and isn't even really needed in the
5.10.y kernel tree yet, as there are no users of the new field.  So
revert it for now.  If it is needed, it can be brought back in an
abi-safe way in the future.

Bug: 161946584
Change-Id: Ibff0d5602c36121fdb31767fd37a013bd26f94cb
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>