brcmfmac: Fix off by one bug in brcmf_count_20mhz_channels()

In the brcmf_count_20mhz_channels function we are looping through a list
of channels received from firmware. Since the index of the first channel
is 0 the condition leads to an off by one bug. This is causing us to hit
the WARN_ON_ONCE(1) calls in the brcmu_d11n_decchspec function, which is
how I discovered the bug.

Introduced by:
commit b48d8916
("brcmfmac: rework wiphy structure setup")
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c

@@ -4921,7 +4921,7 @@ static void brcmf_count_20mhz_channels(struct brcmf_cfg80211_info *cfg,
 	struct brcmu_chan ch;
 	int i;
 
-	for (i = 0; i <= total; i++) {
+	for (i = 0; i < total; i++) {
 		ch.chspec = (u16)le32_to_cpu(chlist->element[i]);
 		cfg->d11inf.decchspec(&ch);