Update blkdev_get_by_dev calls to accommodate new holder ops argument

[mbaehr]

This is necessary to build on kernel 6.5 (installed w/ today's Ubuntu 23.10 release)

[mbaehr]

@SergeiShtepa I am not sure if this is up to your coding standards but I wanted to let you know it did get me a successfully-building module on Ubuntu 23.10 w/ kernel 6.5.

As I am using ZFS, I have not yet actually able to test the blksnap functionality to be sure there is no regression in functionality w/ this kernel series. I intend to do further experimentation using a supported filesystem later.

[SergeiShtepa]

Hi!
Thank you for your pull request.

I already support lk 6.5 in the branch VAL-6.1 and merge this fix into VAL-6.0 (I published it only today).
This should work for lk 6.6 as well.

The code from the VAL-6.0 branch is considered stable and is supported by Veeam and I advise you to use it.

In these branches, the module is being developed, which is part of the Veeam Agent for Linux product release 6.0 and next release 6.1. Alas, the master branch is outdated. Perhaps I will update it in the future. I don't know yet.

[SergeiShtepa]

As I am using ZFS, I have not yet actually able to test the blksnap functionality to be sure there is no regression in functionality w/ this kernel series. I intend to do further experimentation using a supported filesystem later.

Let me remind you that the main task of the blksnap project is to create a patch for the Linux kernel upstream.
You can familiarize with it here. Tools for working with this version of the blksnap module are available in the branch.
I'm still testing this code. THIS IS UNSTABLE CODE.
I would appreciate it if you could find an opportunity to check the compatibility of the blksnap module with ZFS. It looks like fallocate has been supported. But alas, I have no plans to test compatibility with ZFS.