brcmfmac: Remove error print for invalid key index.

When a key is set or cleared with an unsupported key index then
brcmfmac will print an error. With most wpa_supplicants this is
happening a lot. The error print is confusing and not needed.
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c

@@ -2252,7 +2252,6 @@ brcmf_cfg80211_del_key(struct wiphy *wiphy, struct net_device *ndev,
 
 	if (key_idx >= BRCMF_MAX_DEFAULT_KEYS) {
 		/* we ignore this key index in this case */
-		brcmf_err("invalid key index (%d)\n", key_idx);
 		return -EINVAL;
 	}