iommu/arm-smmu: Fix error checking for ASID and VMID allocation

iommu/arm-smmu: Fix error checking for ASID and VMID allocation

commit c0733a2cf30c1e7923b6ad4f8df67941502923de upstream.

The bitmap allocator returns an int, which is one of the standard
negative values on failure. Rather than assigning this straight to a
u16 (like we do for the ASID and VMID callers), which means that we
won't detect failure correctly, use an int for the purposes of error
checking.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>