Revert "loop: Avoid updating block size under exclusive owner"

This reverts commit ce8da5d1 which is
commit 7e495382 upstream.

It breaks the Android tests for some reason and can be brought back in
the future in an safe way if it is really needed.

Change-Id: I91c20b05df1a5e8827e52502c5c52a72b8633813
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>