iommu/vt-d: Support Enhanced Command Interface

iommu/vt-d: Support Enhanced Command Interface

The Enhanced Command Register is to submit command and operand of
enhanced commands to DMA Remapping hardware. It can supports up to 256
enhanced commands.

There is a HW register to indicate the availability of all 256 enhanced
commands. Each bit stands for each command. But there isn't an existing
interface to read/write all 256 bits. Introduce the u64 ecmdcap[4] to
store the existence of each enhanced command. Read 4 times to get all of
them in map_iommu().

Add a helper to facilitate an enhanced command launch. Make sure hardware
complete the command. Also add a helper to facilitate the check of PMU
essentials. These helpers will be used later.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230128200428.1459118-4-kan.liang@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>