Revert "zram: register default groups with device_add_disk()"

This reverts commit 70a534ad.

The patch series submitted for the 4.19-stable branch:
	https://lore.kernel.org/r/20210223092859.17033-1-jefflexu@linux.alibaba.com


should be reverted from the android-4.19-stable branch as it breaks the
ABI for device_add_disk() and the issue the series is resolving does not
affect Android devices.  So revert the whole thing.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I36971c96eb15cdf64709d1fa3186cd107946b541