LU-9480 lnet: rename lnet_add/del_peer_ni_to/from_peer()

LU-9480 lnet: rename lnet_add/del_peer_ni_to/from_peer()

Rename lnet_add_peer_ni_to_peer() to lnet_add_peer_ni(), and
lnet_del_peer_ni_from_peer() to lnet_del_peer_ni().  This brings
the function names closer to the ioctls they implement:
IOCTL_LIBCFS_ADD_PEER_NI and IOCTL_LIBCFS_DEL_PEER_NI. These
names are also a more accturate description their effect: adding
or deleting an lnet_peer_ni to LNet.

Test-Parameters: trivial
Signed-off-by: Olaf Weber <olaf@sgi.com>
Change-Id: I0eefb60cbdedb998a659002b48d4c8ddd3b11fb2
Reviewed-on: https://review.whamcloud.com/25778
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Tested-by: Amir Shehata <amir.shehata@intel.com>