LU-16508 netlink: resv_start_op for [lnet|lustre]_family

LU-16508 netlink: resv_start_op for [lnet|lustre]_family

Linux v5.0-11693-g3b0f31f2b8c9
  genetlink: make policy common to family

struct genl_family adds policy and resv_start_op members

Linux v6.1-rc2-63-g4fa86555d1cd
  genetlink: piggy back on resv_op to default to a reject policy

struct genl_family needs to set a policy and/or indicate the
commands that should be validated.

Set the resv_start_op higher than the largest command accepted.
to avoid a default policy of NLA_REJECT.

When genl_family has a policy provide one.

HPE-bug-id: LUS-11454
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: If38fbe4c9358bb4f9b57e7d25b8a6df1fba63452
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49800
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: xinliang <xinliang.liu@linaro.org>