iommu/amd: Take domain->lock for complete attach/detach path

The code-paths before __attach_device() and __detach_device() are called
also access and modify domain state, so take the domain lock there too.
This allows to get rid of the __detach_device() function.

Fixes: 92d420ec

 ("iommu/amd: Relax locking in dma_ops path")
Reviewed-by: Filippo Sironi <sironi@amazon.de>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>