Staging: heci: fix userspace pointer mess

Fix userspace pointer mess.
 - In memcmp(), dest and src pointer should be both in kernel space.
 - Add (void __user *) modification before userspace pointer.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>