SMMU: basic driver for init and probing

Introducing the driver in kernel for detecting SMMU features
and initialise the hardware.

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

Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

cmake: use snake_case for RegisterDriver & CPPFile

Our upcoming cmake styling tool requires any custom functions you want
styled nicely to be lower case. We only need to style these two nicely,
as they have kwargs we would like aligned.

timer-refactor: Move kernel timers and rename

This change moves all arm platform timers to drivers/timer
and renames them to the compatibility string specified in the dts.
Now the correct timer is included at build time based on the dts,
this follows the same pattern as the serial-refactor.
Have moved the arm generic_timer and priv_timer into the timer
folder and updated cmake configs appropriately.

serial-refactor: Fixed circular includes

Modify hardware_gen script to only include chosen
serial path. Added newlines to serial drivers to fix
concat issues when compiling. Move cmake macro RegisterDriver
up a level to support timer refactor. Modify arm cmake to reflect
this.