drm/i915/mtl: Skip using vbt hdmi_level_shifter selection on MTL

The hdmi_level_shifter part of General Bytes definition in VBT, which was
used for choosing different levels on earlier platforms is now a hidden
optin and shows the default value of 0. The level shifter is now to be
deduced from hdmi_default_entry in  intel_ddi_buf_trans for each phy.

Skip providing the default hw provided value to force driver to choose hdmi
default entry.

Bspec: 20124
Cc: Khaled Almahallawy <khaled.almahallawy@intel.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230616210028.1601533-1-radhakrishna.sripada@intel.com