* Implement a SoC probe function, from Linux, which determines the
SoC family, type and revision. This only probes the AR71xx series
SoC and (currently) panics on others.
* Migrate some of the AR71XX specific hardware init (USB device, determining
system frequencies) into using the cpuops introduced in an earlier commit.
Other SoC specific hardware stuff (per-device flush/WB, GPIO pin wiring,
Ethernet PLL setup, other things I've likely missed) will be introduced in
subsequent commits.
Reviewed by: imp@
Obtained from: (partially) Linux
