It's not really scary to even enable it forever.  After all it's i8259,
and it's even not the kernel one.

Then we can remove quite a few of lines to make it cleaner.  And "info
irq" will always work for it.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20171210063819.14892-3-peterx@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>