LU-10391 lnet: track pinginfo size in bytes, not nis.

LU-10391 lnet: track pinginfo size in bytes, not nis.

When we extend the pinginfo to be able to store large-address nids,
there could be nids of different sizes in it.  So using the number of
nis to track the size won't work.  So change to using the number of
bytes.  i.e.  the total size of the 'struct lnet_ping_info'.

This affects pb_nnis in the ping_buffer, and the global
ln_push_target_nnis.

LNET_PING_INFO_SIZE is removed as size won't depend on number of nids
any more.

When determining the number of bytes expected in a received ping_info,
use a new macro lnet_ping_info_size() which can extract information
as required from the ping_info.

Note that lnet_ping_target_create() now initializes pi_nis to 0.
Setting the initial size doesn't seem to be useful.

Test-Parameters: trivial testlist=sanity-lnet
Test-Parameters: serverversion=2.12 serverdistro=el7.9 testlist=runtests
Test-Parameters: clientversion=2.12 testlist=runtests
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I7727b784ed9a7510959d5ec41f8df3851adb78ed
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/44627
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: jsimmons <jsimmons@infradead.org>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>