Convert bxt_ddi_phy_set_signal_levels() to act as the full
.set_signal_levels() hook instead of going through a pointless wrapper.
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211001130107.1746-6-ville.syrjala@linux.intel.com