x86, mrst: Remove X86_MRST dependency on PCI_IOAPIC

PCI_IOAPIC is used for PCI hotplug, Moorestown does not have ACPI PCI
hotplug, as it does not have ACPI.  This unnecessary dependency causes
X86_MRST fail to be selected if ACPI is not selected.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
LKML-Reference: <1267550368-7435-1-git-send-email-jacob.jun.pan@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>