Revert "zram: close udev startup race condition as default groups"

This reverts commit 9e07f4e2.

The original commit is actually a "merged" fix of [1] and [2], as
described in [3]. Since now we have more fixes that rely on [1], revert
this commit first, and then get the original [1] and [2] merged.

[1] fef912bf860e, block: genhd: add 'groups' argument to device_add_disk
[2] 98af4d4df889, zram: register default groups with device_add_disk()
[3] https://www.spinics.net/lists/stable/msg442196.html



Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>