iommu/amd: Fix kerneldoc comments

Fix W=1 compile warnings (invalid kerneldoc):

    drivers/iommu/amd/init.c:1586: warning: Function parameter or member 'ivrs' not described in 'get_highest_supported_ivhd_type'
    drivers/iommu/amd/init.c:1938: warning: Function parameter or member 'iommu' not described in 'iommu_update_intcapxt'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200728170859.28143-1-krzk@kernel.org


Signed-off-by: Joerg Roedel <jroedel@suse.de>