staging: brcm80211: bugfix for len==0 parameter in 3 fullmac functions

Three functions use the same method to check incoming parameters. The
'len' parameter can be equal to 0 in case of a 'set' operation.
Currently these functions return an error code under that condition,
which is incorrect. The problem was introduced in recent patches in
which asserts were removed from the fullmac.

Despite this being a bug, my regression testing has not shown any problems.
Reported-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NRoland Vossen <rvossen@broadcom.com>
Reviewed-by: NArend van Spriel <arend@broadcom.com>
Reviewed-by: NFranky Lin <frankyl@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/brcm80211/brcmfmac/bcmsdh_sdmmc.c

@@ -407,7 +407,7 @@ brcmf_sdioh_iovar_op(struct sdioh_info *si, const char *name,
 	bool bool_val;
 	u32 actionid;
 
-	if (name == NULL || len <= 0)
+	if (name == NULL || len < 0)
 		return -EINVAL;
 
 	/* Set does not take qualifiers */

drivers/staging/brcm80211/brcmfmac/dhd_common.c

@@ -311,7 +311,7 @@ brcmf_c_iovar_op(struct brcmf_pub *drvr, const char *name,
 
 	BRCMF_TRACE(("%s: Enter\n", __func__));
 
-	if (name == NULL || len <= 0)
+	if (name == NULL || len < 0)
 		return -EINVAL;
 
 	/* Set does not take qualifiers */

drivers/staging/brcm80211/brcmfmac/dhd_sdio.c

@@ -3123,7 +3123,7 @@ brcmf_sdbrcm_bus_iovar_op(struct brcmf_pub *drvr, const char *name,
 
 	BRCMF_TRACE(("%s: Enter\n", __func__));
 
-	if (name == NULL || len <= 0)
+	if (name == NULL || len < 0)
 		return -EINVAL;
 
 	/* Set does not take qualifiers */