LU-16796 llite: Change struct pcc_dataset to use kref

LU-16796 llite: Change struct pcc_dataset to use kref

This patch changes struct pcc_dataset to use
kref instead of atomic_t

Test-Parameters: trivial testlist=sanity-pcc
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Id9f7521a999be5917ce03a0ec4572091b2043c3f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56121
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Qian Yingjin <qian@ddn.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>