sysutils/devcpu-data Unbreak build by using a cached distfile for amd microcode.

Use a freebsd.org hosted version of the amd microcode file fetched
in February of 2015. The amd64.org site has been down for a long time and
probably will never come back.

Reported by: netchild
Reviewed by: mat antoine
Approved by: portmgr (mat@ antoin@)
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D13792