sysutils/devcpu-data: Provide a file for loading Intel updates at boot

Extend the port so that users may easily apply microcode updates using
the method implemented in src r337715. For now, this just consists of
providing all Intel microcode update files concatenated together as a
single blob in /boot/firmware.

Approved by: sbruno
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D16924