drm/i915/xe2hpd: Set maximum DP rate to UHBR13.5

Max supported speed by xe2hpd is UHBR13.5. Limit the max DP source rate
to it.

Bspec: 67066
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Shekhar Chauhan <shekhar.chauhan@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240430172850.1881525-16-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/display/intel_dp.c

@@ -477,6 +477,9 @@ static int mtl_max_source_rate(struct intel_dp *intel_dp)
 	if (intel_encoder_is_c10phy(encoder))
 		return 810000;
 
+	if (DISPLAY_VER_FULL(to_i915(encoder->base.dev)) == IP_VER(14, 1))
+		return 1350000;
+
 	return 2000000;
 }