iwlwifi: Sanity check for sta_id

On my testing, I saw some strange behavior

[  421.739708] iwlwifi 0000:01:00.0: ACTIVATE a non DRIVER active station id 148 addr 00:00:00:00:00:00
[  421.739719] iwlwifi 0000:01:00.0: iwl_sta_ucode_activate Added STA id 148 addr 00:00:00:00:00:00 to uCode

not sure how it happen, but adding the sanity check to prevent memory
corruption

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
iwl_sta_alloc_lq(struct iwl_priv *priv, struct iwl_rxon_context *ctx,
		 u8 sta_id)
{
	struct iwl_link_quality_cmd *link_cmd;

	link_cmd = kzalloc(sizeof(struct iwl_link_quality_cmd), GFP_KERNEL);
	if (!link_cmd) {
		IWL_ERR(priv, "Unable to allocate memory for LQ cmd.\n");
		return NULL;
	}

	iwl_sta_fill_lq(priv, ctx, sta_id, link_cmd);

	return link_cmd;
}

iwl_sta_alloc_lq(struct iwl_priv *priv, struct iwl_rxon_context *ctx,
		 u8 sta_id)
{
	struct iwl_link_quality_cmd *link_cmd;

	link_cmd = kzalloc(sizeof(struct iwl_link_quality_cmd), GFP_KERNEL);
	if (!link_cmd) {
		IWL_ERR(priv, "Unable to allocate memory for LQ cmd.\n");
		return NULL;
	}

	iwl_sta_fill_lq(priv, ctx, sta_id, link_cmd);

	return link_cmd;
}
