Convert to SPDX license tags

Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

trivial: Style changed files

libsel4vm: 'restart_vcpu_fault' in fault interface

Added 'restart_vcpu_fault' in the vcpu fault interface. This
giving the user the ability to re-execute the faulting
instruction.

libsel4vm: Removed uses of 'vmm' in x86 source

Updated x86 source such that the naming convention used is to
prefix/postfix with 'vm' rather than 'vmm'. This change makes
the naming convention consistent as this library now represents a
single 'vm' instance rather than a vmm.

libsel4vm: arch specific includes into arch subdir

Moved the architecture specific headers, being unique header files
that only exist for a given architecture, into an 'arch'
subdirectory. Since this library can be used across architectures
this avoids polluting the root libsel4vm namespace and adds
further structure to distinguish different interfaces.

libsel4vm: Moved remaining x86 platform includes

Moved the remaining x86 platform includes [vmcs.h and vmexit.h]
into the x86 arch include directory. This are still relevant to
to this library and not necessarily platform specific (such that
it should exist libsel4vmmplatsupport).

libsel4vm: x86 processor src as private interface

Moved the x86 processor source and header into the x86
architecture subdirectory. This has been transformed into an
private interface that only internal code can access. We choose
to abstract over processor source. Updated the processor header
includes to reflect this change.

libsel4vm: Removed x86 vmm.h

This header is no longer needed as it doesn't contain any
definitions. Updated source to remove usages of vmm.h includes
and where necessary repaired missing includes (that vmm.h would
otherwise provide).

libsel4vm: Removed vmm_[read|set]_user_context

This is now implemented by the guest x86 context interface.
Updates source to use 'vm_[get|set]_thread_context_reg'.

libsel4vm: Make guest_state interface private

Make the guest_state interface a private header as we don't want
to expose this to the user. Updated the internal source to include
the private header.

libsel4vm: Make x86 vcpu guest state a pointer

Updated the reference to the guest state datastructure to be a
pointer. This being allocated at initialisation time. In addition
update all references of the guest state datastructure to reflect
the type change. This change stages way for making the guest state
datastructure a private interface.

libsel4vm: Consolidated VCPU fault interface

Added a new utility interface to extract general fault information
out of a vcpu object. This abstracts the architecture specific
interfaces for retrieving fault information. This interface is
introduced such that the architecture specific interfaces can
be made private and to also create a utility that future drivers
can use across different platforms.