iommu/arm-smmu: fix iommu_present() test in init

The extra semi-colon on the end breaks the test.

Cc: <stable@vger.kernel.org>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>