btl/usnic: s/get_nsec/get_nticks/g

Rename "get_nsec()" to "get_ticks()" to more accurately reflect that
this function has no correlation to wall clock time at all.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
(cherry picked from commit ce2910a28aea61043b81324c67999f3a47cfe7ac)

opal/mca/btl/usnic/btl_usnic.h

@@ -68,7 +68,7 @@ extern uint64_t opal_btl_usnic_ticks;
 extern opal_recursive_mutex_t btl_usnic_lock;
 
 static inline uint64_t
-get_nsec(void)
+get_ticks(void)
 {
     return opal_btl_usnic_ticks;
 }

opal/mca/btl/usnic/btl_usnic_module.c

@@ -1236,7 +1236,7 @@ opal_btl_usnic_module_progress_sends(
 
         /* Is it time to send ACK? */
         if (endpoint->endpoint_acktime == 0 ||
-            endpoint->endpoint_acktime <= get_nsec()) {
+            endpoint->endpoint_acktime <= get_ticks()) {
             if (OPAL_LIKELY(opal_btl_usnic_ack_send(module, endpoint) == OPAL_SUCCESS)) {
                 opal_btl_usnic_remove_from_endpoints_needing_ack(endpoint);
             } else {

opal/mca/btl/usnic/btl_usnic_recv.h

@@ -114,7 +114,7 @@ opal_btl_usnic_update_window(
 
     /* give this process a chance to send something before ACKing */
     if (0 == endpoint->endpoint_acktime) {
-        endpoint->endpoint_acktime = get_nsec() + 50000;    /* 50 usec */
+        endpoint->endpoint_acktime = get_ticks() + 50000;
     }
 
     /* Save this incoming segment in the received segmentss array on the