x86, iommu: Utilize the IOMMU_INIT macros functionality.

We remove all of the sub-platform detection/init routines and instead
use on the .iommu_table array of structs to call the .early_init if
.detect returned a positive value. Also we can stop detecting other
IOMMUs if the IOMMU used the _FINISH type macro. During the
'pci_iommu_init' stage, we call .init for the second-stage
initialization if it was defined. Currently only SWIOTLB has this
defined and it used to de-allocate the SWIOTLB if the other detected
IOMMUs have deemed it unnecessary to use SWIOTLB.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <1282845485-8991-11-git-send-email-konrad.wilk@oracle.com>
CC: Fujita Tomonori <fujita.tomonori@lab.ntt.co.jp>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>