thunderbolt: Initialize after IOMMUs

If IOMMU is enabled and Thunderbolt driver is built into the kernel
image, it will be probed before IOMMUs are attached to the PCI bus.
Because of this DMA mappings the driver does will not go through IOMMU
and start failing right after IOMMUs are enabled.

For this reason move the Thunderbolt driver initialization happen at
rootfs level.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>