aarch64: arch-switch: implement switch to first

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: implement page fault, fixup, backtrace

implement page fault handling, including fixup fault,
and backtrace which is the first simple user.

Signed-off-by: Jani Kokkonen <jani.kokkonen@huawei.com>

[claudio: added elf changes to allow lookup and demangling to work]

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: loader: allow execution to main_cont

allow execution to flow until main_cont
so we can reach the backtrace.

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