staging: wilc1000: use kmemdup in host_int_add_ptk

This patch changes kmalloc followed by memcpy to kmemdup
The error checking is also added when kmemdup is failed.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>