aarch64: gic: implement GICv2

implement simple GIC class for interacting with
the GIC distributor and CPU interface.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: exceptions: implement interrupt table

implement a simple interrupt table to register interrupt IDs
and handlers. Map the GIC so it can be initialized by the
table constructor.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: smp: prepare GIC initialization per cpu

arch::init_on_cpu should initialize the gic cpu interface,
but not for the boot CPU, for which this has already been
done.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: implement basic General Timers infrastructure

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: implement exception entry and exit

generate exception frame

Signed-off-by: Jani Kokkonen <jani.kokkonen@huawei.com>
Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
bits and pieces to go a bit forward

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>