x86, apic: Allow to use certain functions without APIC built-in support

In case even if the kernel is configured so that
no APIC support is built-in we still may allow
to use certain apic functions as dummy calls.

In particular we start using it in perf-events code.

Note that this is not that same as NOOP apic driver (which
is used if APIC support is present but no physical APIC is
available), this is for the case when we don't have apic code
compiled in at all.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20100317104356.011052632@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>