sysutils/devcpu-data: Revert back to legacy microcode.dat implementation.

Either there is a problem with the Intel supplied microcode files or
cpucontrol does not yet understand how to process a micrcode update file
with multiple entries. For now, abort.

Reviewed by: swills
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D13987