iwlwifi: mvm: fix off-by-one in scan channels configuration

tail should be equal to the last valid index, so
decrease it by one.

This error causes in "a gap" in some cases (as well as
some possible out-of-bound write), finally resulting in
ucode assertion.
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/scan.c

@@ -732,7 +732,7 @@ int iwl_mvm_config_sched_scan(struct iwl_mvm *mvm,
 	int band_2ghz = mvm->nvm_data->bands[IEEE80211_BAND_2GHZ].n_channels;
 	int band_5ghz = mvm->nvm_data->bands[IEEE80211_BAND_5GHZ].n_channels;
 	int head = 0;
-	int tail = band_2ghz + band_5ghz;
+	int tail = band_2ghz + band_5ghz - 1;
 	u32 ssid_bitmap;
 	int cmd_len;
 	int ret;