x86/setup: Remove unused MCA variables

Commit

  bb8187d3 ("MCA: delete all remaining traces of microchannel bus support.")

removed the remaining traces of Micro Channel Architecture support but
one trace remained - three variables in setup.c which have been unused
since 2012 at least.

Drop them finally.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201021165614.23023-1-bp@alien8.de

arch/x86/kernel/setup.c

@@ -119,11 +119,6 @@ EXPORT_SYMBOL(boot_cpu_data);
 
 unsigned int def_to_bigsmp;
 
-/* For MCA, but anyone else can use it if they want */
-unsigned int machine_id;
-unsigned int machine_submodel_id;
-unsigned int BIOS_revision;
-
 struct apm_info apm_info;
 EXPORT_SYMBOL(apm_info);