iommu/vt-d: Don't dereference iommu_device if IOMMU_API is not built

commit 9def3b1 upstream.

Since commit c40aaaa ("iommu/vt-d: Gracefully handle DMAR units
with no supported address widths") dmar.c needs struct iommu_device to
be selected. We can drop this dependency by not dereferencing struct
iommu_device if IOMMU_API is not selected and by reusing the information
stored in iommu->drhd->ignored instead.

This fixes the following build error when IOMMU_API is not selected:

drivers/iommu/dmar.c: In function ‘free_iommu’:
drivers/iommu/dmar.c:1139:41: error: ‘struct iommu_device’ has no member named ‘ops’
 1139 |  if (intel_iommu_enabled && iommu->iommu.ops) {
                                                ^

Fixes: c40aaaa ("iommu/vt-d: Gracefully handle DMAR units with no supported address widths")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20201013073055.11262-1-brgl@bgdev.pl
Signed-off-by: Joerg Roedel <jroedel@suse.de>
[ - context change due to moving drivers/iommu/dmar.c to
    drivers/iommu/intel/dmar.c
  - set the drhr in the iommu like in upstream commit b1012ca
    ("iommu/vt-d: Skip TE disabling on quirky gfx dedicated iommu") ]
Signed-off-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/iommu/dmar.c

@@ -1087,6 +1087,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 	raw_spin_lock_init(&iommu->register_lock);
 
 	drhd->iommu = iommu;
+	iommu->drhd = drhd;
 
 	if (intel_iommu_enabled && !drhd->ignored)
 		iommu->iommu_dev = iommu_device_create(NULL, iommu,
@@ -1104,7 +1105,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
 static void free_iommu(struct intel_iommu *iommu)
 {
-	if (intel_iommu_enabled && iommu->iommu_dev)
+	if (intel_iommu_enabled && !iommu->drhd->ignored)
 		iommu_device_destroy(iommu->iommu_dev);
 
 	if (iommu->irq) {

include/linux/intel-iommu.h

@@ -447,6 +447,8 @@ struct intel_iommu {
 	struct device	*iommu_dev; /* IOMMU-sysfs device */
 	int		node;
 	u32		flags;      /* Software defined flags */
+
+	struct dmar_drhd_unit *drhd;
 };
 
 static inline void __iommu_flush_cache(