drm/i915/mtl: Calculate the correct voltage level from port_clock

On MTL we need to bump the voltage level to only 1 (not 2)
when port clock exceeds 594MHz. Make it so.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231128115138.13238-8-ville.syrjala@linux.intel.com


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