UPSTREAM: zram: avoid lockdep splat by revalidate_disk

(cherry-pick from commit b4c5c60920e3b0c4598f43e7317559f6aec51531)

Sasha reported lockdep warning [1] introduced by [2].

It could be fixed by doing disk revalidation out of the init_lock.  It's
okay because disk capacity change is protected by init_lock so that
revalidate_disk always sees up-to-date value so there is no race.

[1] https://lkml.org/lkml/2014/7/3/735


[2] zram: revalidate disk after capacity change

Fixes 2e32baea46ce ("zram: revalidate disk after capacity change").

Bug: 25951511

Change-Id: Id4498d2993849b57bf37b2fa17470c39e8837b58
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: "Alexander E. Patrakov" <patrakov@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>