iommu/tegra-smmu: Fix invalid ASID bits on Tegra30/114

Both Tegra30 and Tegra114 have 4 ASID's and the corresponding bitfield of
the TLB_FLUSH register differs from later Tegra generations that have 128
ASID's.

In a result the PTE's are now flushed correctly from TLB and this fixes
problems with graphics (randomly failing tests) on Tegra30.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>