iommupt: Fix the kunit building

The kunit doesn't work since the below commit made GENERIC_PT
unselectable:

 $ make ARCH=x86_64 O=build_kunit_x86_64 olddefconfig
 ERROR:root:Not all Kconfig options selected in kunitconfig were in the generated .config.
 This is probably due to unsatisfied dependencies.
 Missing: CONFIG_DEBUG_GENERIC_PT=y, CONFIG_IOMMUFD_TEST=y,
 CONFIG_IOMMU_PT_X86_64=y, CONFIG_GENERIC_PT=y, CONFIG_IOMMU_PT_AMDV1=y,
 CONFIG_IOMMU_PT_VTDSS=y, CONFIG_IOMMU_PT=y, CONFIG_IOMMU_PT_KUNIT_TEST=y

Also remove the unneeded CONFIG_IOMMUFD_TEST reference as the iommupt kunit
doesn't interact with iommufd, and it doesn't currently build for the
kunit due problems with DMA_SHARED buffer either.

Fixes: 01569c21 ("genpt: Make GENERIC_PT invisible")
Fixes: 1dd4187f ("iommupt: Add a kunit test for Generic Page Table")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>