mac80211: Remove unused 'len' variable

Commit 633e2713 (mac80211: split sched scan IEs) introduced the
len variable to keep track of the return value of
ieee80211_build_preq_ies() but did not use it. Compiling with W=1
gives the following warning, fix it.

net/mac80211/scan.c: In function ‘__ieee80211_request_sched_scan_start’:
net/mac80211/scan.c:1123:9: warning: variable ‘len’ set but not used [-Wunused-but-set-variable]

This is a harmless warning and is only being fixed to reduce the noise
with W=1 in the kernel.

Fixes: 633e2713 ("mac80211: split sched scan IEs")
Cc: David Spinadel <david.spinadel@intel.com>
Cc: Alexander Bondar <alexander.bondar@intel.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kirtika Ruchandani <kirtika@chromium.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/scan.c

@@ -1120,7 +1120,6 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
 	u32 rate_masks[NUM_NL80211_BANDS] = {};
 	u8 bands_used = 0;
 	u8 *ie;
-	size_t len;
 
 	iebufsz = local->scan_ies_len + req->ie_len;
 
@@ -1145,10 +1144,9 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
 
 	ieee80211_prepare_scan_chandef(&chandef, req->scan_width);
 
-	len = ieee80211_build_preq_ies(local, ie, num_bands * iebufsz,
-				       &sched_scan_ies, req->ie,
-				       req->ie_len, bands_used,
-				       rate_masks, &chandef);
+	ieee80211_build_preq_ies(local, ie, num_bands * iebufsz,
+				 &sched_scan_ies, req->ie,
+				 req->ie_len, bands_used, rate_masks, &chandef);
 
 	ret = drv_sched_scan_start(local, sdata, req, &sched_scan_ies);
 	if (ret == 0) {