iommu/arm-smmu: add support for DOMAIN_ATTR_DYNAMIC

Implement support for dynamic domain switching.  This feature is
only enabled when the qcom,dynamic device tree attribute for an smmu
instance.

In order to use dynamic domains, a non-dynamic domain must first
be created and attached.  This non-dynamic domain must remain
attached while the device is in use.

All domains must be attached before calling any mapping functions, such as
iommu_map(). This allows the pagetable setup to be set up during attach
based on the hardware configuration for the smmu.

Before attaching a dynamic domain, the DOMAIN_ATTR_CONTEXT_BANK must be
set to indicate which context bank registers should be used for
any register programming.  Attaching dynamic domain doesn't cause
hardware register programming, but mapping operations may cause
TLBI operations. Additionally, the upstream driver or hardware may
do other register programming.

Because the arm-smmu driver assigns context banks dynamically, the
upstream driver should query DOMAIN_ATTR_CONTEXT_BANK on its non-dynamic
domain, to ensure the correct value is used for all dynamic domains
created.

To switch domains dynamically, the upstream driver or hardware
must program the TTBR0 and CONTEXTIDR registers with the values
from the DOMAIN_ATTR_TTBR0 and DOMAIN_ATTR_CONTEXTIDR attributes
for the desired domain. The upstream driver may also need to do
other hardware specific register programming to properly
synchronize the domain switch. It must ensure that all register
state, except for CONTEXTIDR and TTBR0 registers, is restored
at the end of the domain switch operation.

DOMAIN_ATTR_PROCID may be set to any value for each domain
before it is attached. This value is part of the CONTEXTIDR
register, but it is not used by the SMMU hardware. Setting a unique
value for this attribute in every domain can be useful for debugging.

Change-Id: Ib92d06db06832700bdf56265b169ccddfb192698
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>