LU-16796 ptlrpc: Change struct nrs_tbf_rule to use kref

LU-16796 ptlrpc: Change struct nrs_tbf_rule to use kref

This patch changes struct nrs_tbf_rule to use
kref instead of atomic_t

Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ia716655f98046787c51d2f581f2c88979a50b25b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56193
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>