iommu/amd: Set iommu->int_enabled consistently when interrupts are set up

When I made the INTCAPXT support stop gratuitously pretending to be MSI,
I missed the fact that iommu_setup_msi() also sets the ->int_enabled
flag. I missed this in the iommu_setup_intcapxt() code path, which means
that a resume from suspend will try to allocate the IRQ domains again,
accidentally re-enabling interrupts as it does, resulting in much sadness.

Lift out the bit which sets iommu->int_enabled into the iommu_init_irq()
function which is also where it gets checked.

Link: https://lore.kernel.org/r/20210104132250.GE32151@zn.tnic/
Fixes: d1adcfbb ("iommu/amd: Fix IOMMU interrupt generation in X2APIC mode")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/50cd5f55be8ead0937ac315cd2f5b89364f6a9a5.camel@infradead.orgSigned-off-by: Will Deacon <will@kernel.org>

drivers/iommu/amd/init.c

@@ -1973,8 +1973,6 @@ static int iommu_setup_msi(struct amd_iommu *iommu)
 		return r;
 	}
 
-	iommu->int_enabled = true;
-
 	return 0;
 }
 
@@ -2169,6 +2167,7 @@ static int iommu_init_irq(struct amd_iommu *iommu)
 	if (ret)
 		return ret;
 
+	iommu->int_enabled = true;
 enable_faults:
 	iommu_feature_enable(iommu, CONTROL_EVT_INT_EN);