trivial: style and comment

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: TLB coherency between MMU and SMMU

The kernel connects ASID used in MMU and context banks used in
SMMU, and conducts TLB invalidation on context banks if a page
entry is invalidated from MMU is also used in SMMU.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: supporting probing fault status

Providing system calls that enquiry the fault status in context
banks and in SMMU overall.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: supporting deletion on stream ID caps

Providing support to delete stream ID caps and remove any assigned
context banks to deleted stream ID caps.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: supporting unbind context banks

Providing system calls on stream ID caps that unbinds its
context banks. Any future transaction using this stream ID
will result on faluts.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: supporting unassign vspace in context banks

Providing a system call that removes an assigned vspace root from its
context bank. This operation causes the context bank being disabled
as it does not have a valid vspace root after the unassignment.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: removing mapped attribute from SMMU caps

The mapped attributes in both context bank and stream ID caps
are reundant for maintaining the semantics on those caps.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: TLB invalidation system calls

Providing system calls for conducting TLB invalidation operations
on all TLB entries or entries in a context bank.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: binding stream ID to context banks

Providing system calls that binds context banks to stream IDs.
Once the stream ID is bound, the transaction using that SID is
enabled.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: assigning vspace to context banks

Supporting user-level applications to assign vsapce root to context
banks through system calls. This commit also configures the context
bank according to stage 1 or stage 2 requirement.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: system calls for creating SID and CB caps

Providing system calls on stream ID control cap and context bank
control cap for creating stream ID and context bank caps.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>

SMMU: providing master control caps to root task

Adding the master control caps that are used to create transaction
and context banks caps. This commit includes the internal kernel
structure that required to manage any created transaction and
context bank caps.

Signed-off-by: Oliver Scott <Oliver.Scott@data61.csiro.au>