ANDROID: KVM: arm64: Enable S2MPUs in __pkvm_init_stage2_iommu

Initialize the S2MPU driver in __pkvm_init_stage2_iommu if requested by
the host. The driver sets kvm_iommu_ops and configures all S2MPUs which
are powered on at that point (ie. all S2MPUs on currently supported
devices).

The S2MPU L1ENTRY registers are set to 1G granularity and R/W access.
CTRL0/CTRL1/CFG as set to reasonable defaults, though the code relies on
the reset state blocking all traffic as well.

On fault the S2MPUs are configured to return SLVERR/DECERR (v8/9) to the
master. Interrupts are enabled for all VIDs and trigger an IRQ handler
if EL1 init registered a handler as a result of a DT interrupts entry.

Because the host can configure the SSMTs freely, all permission bits are
configured for all VIDs. For v9 CONTEXT_CFG_VALID_VIDS is set to the
value precomputed at EL1, allocating a context ID to each VID.

Test: builds, boots
Bug: 190463801
Signed-off-by: David Brazdil <dbrazdil@google.com>
Change-Id: I20e658a77c93fa18a07e388d13a639dc67e600d8