FreeBSD/src dee401e (r340421)usr.sbin/cpucontrol cpucontrol.c intel.c

cpucontrol(8): De-duplicate common update logic

Every µcode-updater must open the cpucontrol devfs node RDWR, open a
firmware file, validate the FW file has a positive length, mmap it, etc.
De-duplicate that identical logic between every individual platform.

Also, constify references to the readonly-mapped firmware files while here.

Sponsored by:   Dell EMC Isilon
DeltaFile
+101-44usr.sbin/cpucontrol/cpucontrol.c
+24-50usr.sbin/cpucontrol/intel.c
+20-51usr.sbin/cpucontrol/via.c
+17-45usr.sbin/cpucontrol/amd.c
+11-37usr.sbin/cpucontrol/amd10h.c
+10-1usr.sbin/cpucontrol/cpucontrol.h
+183-2286 files

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