LU-13004 lnet: remove the 'struct kvec' arg from lnd_send

LU-13004 lnet: remove the 'struct kvec' arg from lnd_send

lnd_send() is now always sent a lnet_kiov_t pointer, never a
'struct kvec' pointer.
So remove the option of 'struct kvec *'.

This means that kiblnd_setup_rd_iov() is no longer used, so it can go
too.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I121f5c8c43bd7247748d6e4913c76371e9202219
Reviewed-on: https://review.whamcloud.com/37845
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>