x86/apic: Drop workarounds for Pentium/82489DX erratum

x86/apic: Drop workarounds for Pentium/82489DX erratum

CONFIG_X86_GOOD_APIC is unconditionally selected for 64bit builds.  Drop the
related infrastructure including apic_{read,write}_around(), the former of
which had no effect, and the latter which was an alias of apic_write().

No functional change, as confirmed by diffing the before/after disassembly.
(Three __LINE__ numbers are different, but they are `mov $imm, %reg` as part
of a dprintk() call.)

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <JBeulich@suse.com>