Rebase + remove libopencsd-all.ucl

I'm unsure why the libopencsd needs to exist, it will be used by the userspace hwt tool (D40728) to decode trace data from the CPU.

Is my reading of the code correct where uwptpg == NULL in the new else case because it's only set for userspace maps? If so it means we will call pmap_remove_pt_page.

We could create a version gpiobus_attach_bus that doesn't call bus_attach_children for use by multi-function devices. That would mean all buses are added together for more control.

FreeBSD requires all CPUs to be in the same Inner Shareable domain so using ish is correct. This is the same requirement as Linux.

I don't think we need the fence here. Assuming the compiler doesn't reorder any of the barriers and memory operations then as long as the store in CK_STAILQ_INSERT_TAIL has been observed on another CPU then the stores before CK_STAILQ_INSERT_TAIL will also be observed.

If the firmware doesn't implement the Errata ABI then we may enable a workaround in the kernel even if we don't need to, e.g. when the firmware already has a workaround, or the combination of HW means it's not needed

Fix the LINUX_AT_HWCAP* comments

Update LINUX_AT_COUNT to fix a kernel panic

Rebase on D50906 to move all MRS_ macros to undefined.c

Update based on feedback from @alc