iommu/tegra: Make it explicitly non-modular

The Kconfig currently controlling compilation of this code is:

drivers/iommu/Kconfig:config TEGRA_IOMMU_GART
drivers/iommu/Kconfig:  bool "Tegra GART IOMMU Support"

...meaning that it currently is not being built as a module by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.

We explicitly disallow a driver unbind, since that doesn't have a
sensible use case anyway, and it allows us to drop the ".remove"
code for non-modular drivers.

Since module_init was not in use by this code, the init ordering
remains unchanged with this commit.

We replace module.h with moduleparam.h since the file does actually
declare some module_param() and the easiest way to keep back
compatibility with existing use cases is to leave it as-is for now.

The init function was missing an __init annotation, so it was added.

We also delete the MODULE_LICENSE tag etc. since all that information
was (or is now) contained at the top of the file in the comments.

Cc: Hiroshi Doyu <hdoyu@nvidia.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-tegra@vger.kernel.org
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>