x86: Calgary: fix disable busnum for CalIOC2

The old check we used based on dev->bus->number is wrong for devices on
CalIOC2.  Instead look whether we have an IOMMU table for that bus - if
not, translation is disabled.

Thanks to Murillo Fernandes Bernardes <bernarde@br.ibm.com> for
spotting, suggesting a fix and testing.

Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Acked-by: Murillo Fernandes Bernardes <bernarde@br.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>