Convert to SPDX license tags

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

trivial: Cleanup compiler warnings

trivial: Style changed files

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: 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: Made x86 debug a private interface

Moved the debug source into a private interface. This updates the
location of the source and header. In addition updates includes
of the interface, either deleting them (as its no longer used) or
updating the name.

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: Pass vcpu object on ioport callbacks

Updated the x86 ioport callbacks to pass the faulting vcpu object.
This is useful to pass enable the passing of fault state onto the
receiving callbacks.

libsel4vm: io handler uses registered ioports

Updated the 'vmm_io_instruction_handler' to search and call into
the registered ioports before invoking the unhandled ioport
callback.

libsel4vm: Reintroduced IOPort interface to x86

Reintroduced the IOPort interface to the x86 VM. This is an
architecture specific interface that lets the user register in and
out callbacks for emulation on a specific io port.

libsel4vm: Moved ioport callback registration

Moved the callback registration for unhandled ioports into the
ioports.c file. This is done to keep all the ioports code in a
single location. In additional renamed from 'ioport_callback' to
'unhandled_ioport_callback'

libsel4vm: Moved location of x86 ioports

Moved file location of x86 ioports into the appropriate
x86 architecture subdirectory. Additionally updated file names
from 'io.h' to 'ioports.h'. Updated include references to reflect
change.