arm: tegra: iommu: fix coverity issue

smmu->regs cant be NULL when smmu is not NULL

Bug 1046331

Change-Id: I86c932b1c2eb4f9cd427692824dfb5eaf44227e7
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/142311
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sachin Nikam <snikam@nvidia.com>
GVS: Gerrit_Virtual_Submit
1 file changed