Revert "loop: let set_capacity_revalidate_and_notify update the bdev size"

This reverts commit dddf7150 which is
commit 3b4f85d0 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: I0fee190a34c7d8d7fccf3cd5328caf43d21f2f82
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>