iommu: Stop deferring probe at end of initcalls

The IOMMU subsystem has its own mechanism to not defer probe if driver
support is missing. Now that the driver core supports stopping deferring
probe if drivers aren't built-in (and probed), use the driver core
support so the IOMMU specific support can be removed.

Acked-by: Joerg Roedel <jroedel@suse.de>
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>