iommu/shmobile: Enable the driver on all ARM platforms

Renesas ARM platforms are transitioning from single-platform to
multi-platform kernels using the new ARCH_SHMOBILE_MULTI. Make the
driver available on all ARM platforms to enable it on both ARCH_SHMOBILE
and ARCH_SHMOBILE_MULTI, and increase build testing coverage with
COMPILE_TEST.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Joerg Roedel <joro@8bytes.org>