drm/i915/mtl: Fix voltage_level for cdclk==480MHz

Allow MTL to use voltage level 1 for 480MHz cdclk,
instead of the voltage level 2 that it's currently using.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231128115138.13238-6-ville.syrjala@linux.intel.com


Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>