Introduce a weak function to let the platform code provide the processor voltage in 100mV units. Implement the function on Intel platforms using the MSR_PERF_STATUS msr. On other platforms the processor voltage still reads as unknown. Tested on Intel CFL. The CPU voltage is correctly advertised. Change-Id: I31a7efcbeede50d986a1c096a4a59a316e09f825 Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/43904 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Angel Pons <th3fanbus@gmail.com> Reviewed-by: Jonathan Zhang <jonzhang@fb.com> Reviewed-by: Nico Huber <nico.h@gmx.de>