ARC: boot log: eliminate struct cpuinfo_arc #4: boot log per ISA

 - boot log now clearly per ISA
 - global struct cpuinfo_arc[] elimiated
 - local struct struct arcinfo kept for passing info
   between functions

Tested-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202308162101.Ve5jBg80-lkp@intel.com


Signed-off-by: Vineet Gupta <vgupta@kernel.org>