Make it a little less magical and a little simpler and more hardcoded
so we don't end up with an array that's composed mostly of empty
entries.

v2: Add an enum for the voltage+register values (Ville).
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170822000356.17330-1-rodrigo.vivi@intel.com