ixl(4): Fix handling data passed with ioctl from NVM update tool

From Krzysztof:

Ensure that the entire data buffer passed from the NVM update tool is copied in
to kernel space and copied back out to user space using copyin() and copyout().

PR: 234104
Submitted by: Krzysztof Galazka <krzysztof.galazka@intel.com>
Reported by: Finn <ixbug@riseup.net>
MFC after: 5 days
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D18817