x86: apic: export symbols for extended interrupt LVT functions

This patch adds EXPORT_SYMBOLs to allow OProfile to be built as
module.

Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: oprofile-list <oprofile-list@lists.sourceforge.net>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Barry Kasindorf <barry.kasindorf@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>