brcmfmac: fix static checker warning in pmklist handling

The patch fixes a static checker warning:

   drivers/net/wireless/brcm80211/brcmfmac/cfg80211.c:2965
      brcmf_cfg80211_set_pmksa()
	warn: can 'pmkid_len' be negative?

The answer to the question above is likely no so changing its
type to unsigned is sufficient.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -2932,7 +2932,7 @@ brcmf_update_pmklist(struct net_device *ndev,
 		     struct brcmf_cfg80211_pmk_list *pmk_list, s32 err)
 {
 	int i, j;
-	int pmkid_len;
+	u32 pmkid_len;
 
 	pmkid_len = le32_to_cpu(pmk_list->pmkids.npmkid);
 
@@ -2960,8 +2960,7 @@ brcmf_cfg80211_set_pmksa(struct wiphy *wiphy, struct net_device *ndev,
 	struct brcmf_if *ifp = netdev_priv(ndev);
 	struct pmkid_list *pmkids = &cfg->pmk_list->pmkids;
 	s32 err = 0;
-	int i;
-	int pmkid_len;
+	u32 pmkid_len, i;
 
 	brcmf_dbg(TRACE, "Enter\n");
 	if (!check_vif_up(ifp->vif))
@@ -3000,7 +2999,7 @@ brcmf_cfg80211_del_pmksa(struct wiphy *wiphy, struct net_device *ndev,
 	struct brcmf_if *ifp = netdev_priv(ndev);
 	struct pmkid_list pmkid;
 	s32 err = 0;
-	int i, pmkid_len;
+	u32 pmkid_len, i;
 
 	brcmf_dbg(TRACE, "Enter\n");
 	if (!check_vif_up(ifp->vif))