wifi: avoid kernel-infoleak from struct iw_point

In the Linux kernel, the following vulnerability has been resolved:

wifi: avoid kernel-infoleak from struct iw_point

struct iw_point has a 32bit hole on 64bit arches.

struct iw_point {

void __user *pointer; /* Pointer to the data (in user space) */

__u16 length; /* number of fields or size in bytes */

__u16 flags; /* Optional params */

};

Make sure to zero the structure to avoid disclosing 32bits of kernel data

to user space.