wl12xx: use a bitmask instead of list of booleans in scanned_ch

We were using an array of booleans to mark the channels we had already
scanned.  This was causing a sparse error, because bool is not a type
with defined size.  To fix this, use bitmasks instead, which is much
cleaner anyway.

Thanks Johannes Berg for the idea.

Signed-off-by: Luciano Coelho <coelho@ti.com>
diff --git a/drivers/net/wireless/wl12xx/main.c b/drivers/net/wireless/wl12xx/main.c
index 85cb4da..9663326 100644
--- a/drivers/net/wireless/wl12xx/main.c
+++ b/drivers/net/wireless/wl12xx/main.c
@@ -1423,8 +1423,7 @@
 
 	if (wl->scan.state != WL1271_SCAN_STATE_IDLE) {
 		wl->scan.state = WL1271_SCAN_STATE_IDLE;
-		kfree(wl->scan.scanned_ch);
-		wl->scan.scanned_ch = NULL;
+		memset(wl->scan.scanned_ch, 0, sizeof(wl->scan.scanned_ch));
 		wl->scan.req = NULL;
 		ieee80211_scan_completed(wl->hw, true);
 	}
@@ -3502,6 +3501,10 @@
 	wl->hw->wiphy->max_scan_ie_len = WL1271_CMD_TEMPL_MAX_SIZE -
 			sizeof(struct ieee80211_header);
 
+	/* make sure all our channels fit in the scanned_ch bitmask */
+	BUILD_BUG_ON(ARRAY_SIZE(wl1271_channels) +
+		     ARRAY_SIZE(wl1271_channels_5ghz) >
+		     WL1271_MAX_CHANNELS);
 	/*
 	 * We keep local copies of the band structs because we need to
 	 * modify them on a per-device basis.