intel-iommu: return 0 instead of VTD_FR_RESERVED and remove initialization of context-entry when error occurs

1. When there is no fault, return 0 directly.
2. There is no need to set context-entry to 0 when the access to a
context-entry results in an error.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: add DMAR table to ACPI tables

Expose Intel IOMMU to the BIOS. If object of TYPE_INTEL_IOMMU_DEVICE exists,
add DMAR table to ACPI RSDT table. For now the DMAR table indicates that there
is only one hardware unit without INTR_REMAP capability on the platform.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: add Intel IOMMU emulation to q35 and add a machine option "iommu" as a switch

Add Intel IOMMU emulation to q35 chipset and expose it to the guest.
1. Add a machine option. Users can use "-machine iommu=on|off" in the command
line to enable/disable Intel IOMMU. The default is off.
2. Accroding to the machine option, q35 will initialize the Intel IOMMU and
use pci_setup_iommu() to setup q35_host_dma_iommu() as the IOMMU function for
the pci bus.
3. q35_host_dma_iommu() will return different address space according to the
bus_num and devfn of the device.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: add supports for queued invalidation interface

Add supports for queued invalidation interface, an expended invalidation
interface with extended capabilities.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: add context-cache to cache context-entry

Add context-cache to cache context-entry encountered on a page-walk. Each
VTDAddressSpace has a member of VTDContextCacheEntry which represents an entry
in the context-cache. Since devices with different bus_num and devfn have their
respective VTDAddressSpace, this will be a good way to reference the cached
entries.
Each VTDContextCacheEntry will have a context_cache_gen and the cached entry
is valid only when context_cache_gen equals IntelIOMMUState.context_cache_gen.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: add IOTLB using hash table

Add IOTLB to cache information about the translation of input-addresses. IOTLB
use a GHashTable as cache. The key of the hash table is the logical-OR of gfn
and source id after left-shifting.

Signed-off-by: Le Tan <tamlokveer@gmail.com>