rpm: add dep on xfsprogs-devel for reflink support

rpm: add dep on xfsprogs-devel for reflink support

Support for XFS reflink clone was added in:

  commit 8ed874b39b3c330bbcdff434e08995dbb4467285
  Author: Julio Faracco <jcfaracco@gmail.com>
  Date:   Fri Jul 6 10:43:01 2018 -0300

    storage: Rename btrfsCloneFile to support other filesystems.

  commit 2e11298f938672c5430193277c98b9474a68b1fb
  Author: Julio Faracco <jcfaracco@gmail.com>
  Date:   Fri Jul 6 10:43:00 2018 -0300

    configure: Adding XFS library/headers check.

But these patches missed that the xfs/xfs.h header is not installed
unless you have xfsprogs-devel present.

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>