iommu/arm-smmu-v3: add missing MODULE_DESCRIPTION() macro

With ARCH=arm64, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Fixes: da55da5a

 ("iommu/arm-smmu-v3: Make the kunit into a module")
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240613-md-arm64-drivers-iommu-arm-arm-smmu-v3-v1-1-0e9f7584a5c8@quicinc.com


Signed-off-by: Will Deacon <will@kernel.org>