drm/i915/intel_sdvo: Check fixed_mode->clock against max_dotclock in mode_valid

drm/i915/intel_sdvo: Check fixed_mode->clock against max_dotclock in mode_valid

For LVDS SDVO, mode validation checks the requested mode against the
pipe max dotclock, but does not validate the selected fixed mode clock.

After intel_panel_mode_valid(), get the fixed mode and validate its
clock against the max dotclock.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260430131220.3891497-2-ankit.k.nautiyal@intel.com