The patch below gets rid of io_apic_sync().

io_apic_sync() was introduced in 2.1.104 and it was originally done for
masking and unmasking as well.  Later the unmasking use got removed but the
masking use lingered around.  I dont think it was ever justified to do it
and clearly since the lack of io_apic_sync() didnt break some of the other
writes we do to the IO-APIC registers, it must be unnecessary in the
masking case too.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>