iommu/amd: Fix deadlock in ppr-handling error path

In the error path of the ppr_notifer it can happen that the
iommu->lock is taken recursivly. This patch fixes the
problem by releasing the iommu->lock before any notifier is
invoked. This also requires to move the erratum workaround
for the ppr-log (interrupt may be faster than data in the log)
one function up.

Cc: stable@vger.kernel.org # v3.3, v3.4
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>