locking, x86, iommu: Annotate iommu->register_lock as raw

locking, x86, iommu: Annotate iommu->register_lock as raw

The iommu->register_lock can be taken in atomic context and therefore
must not be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>