Move common logic into a default routine in platform/power that other
platforms can reuse to implement the general default shutdown logic.
Add helper routines to print the cause.
Refactor the platforms that had substantial halt logic to reuse the
default implementation.
Three platforms had basically duplicated logic that just was pulled into
the fdtwalk library. Fix these up to call into those routines instead.
-qemu-virt-arm
-qemu-virt-riscv
-jh7110 (visionfive 2 soc)
A pretty simple mechanism, a list of extensions added to
RISCV_EXTENSION_LIST make variable is expanded to an underscore
delimited string appended to the end of -march=
Pretty simple but it should work for now.
Instead of setting a counter of the number of secondaries to start, have
platform or target code pass in a list of harts to start instead. This
allows for there to be discontinuties in the layout of the cpu harts, or
in the case of some sifive based hardware, hart 0 is otherwise offline.
