qcacld-3.0: Resolve out of bound memory access, while processing setpno

propagation from qcacld-2.0 to qcacld-3.0.

While processing setpno ioctl, there is an out of bound memory
issue when Host is copying ioctl arguments to a local buffer.

While copying ioctl arguments, make sure valid indices are used.

Change-Id: I03078df7135f5f1daf1d9bead7d4410e58fb848a
CRs-Fixed: 1112355

core/hdd/src/wlan_hdd_wext.c

@@ -12212,7 +12212,6 @@ static int __iw_set_pno(struct net_device *dev,
 		return -EINVAL;
 	}
 	qdf_mem_copy(data, extra, (len-1));
-	data[len] = '\0';
 	ptr = data;
 
 	if (1 != sscanf(ptr, " %hhu %n", &value, &offset)) {