drm/i915/display: Skip state verification with TBT-ALT mode

With TBT-ALT mode we are not programming C20 chip PLL's and
hence we don't need to check state verification. We don't
need to program DP link signal levels i.e.pre-emphasis and
voltage swing either.

This patch fixes dmesg errors like this one

"[drm] ERROR PHY F Write 0c06 failed after 3 retries."

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231129122221.1109084-1-mika.kahola@intel.com