CLEANUP: src/listener.c: remove redundant NULL check

fixes #2031

quoting Willy Tarreau:

"Originally the listeners were intended to work without a bind_conf
(e.g. for FTP processing) hence these tests, but over time the
bind_conf has become omnipresent"
diff --git a/src/listener.c b/src/listener.c
index d5390ed..3da01df 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -160,7 +160,7 @@
 		if (!(li->bind_conf->options & BC_O_UNLIMITED)) {
 			HA_ATOMIC_UPDATE_MAX(&global.sps_max,
 			                     update_freq_ctr(&global.sess_per_sec, 1));
-			if (li->bind_conf && li->bind_conf->options & BC_O_USE_SSL) {
+			if (li->bind_conf->options & BC_O_USE_SSL) {
 				HA_ATOMIC_UPDATE_MAX(&global.ssl_max,
 				                     update_freq_ctr(&global.ssl_per_sec, 1));
 			}