x86, irq: Kill io_apic_renumber_irq

Now that the generic irq layer is performing the exact same remapping as
io_apic_renumber_irq we can kill this weird  es7000 specific function.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
LKML-Reference: <1269936436-7039-15-git-send-email-ebiederm@xmission.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>