drm/i915/dp: Return min bpc supported by source instead of 0

Currently, intel_dp_dsc_max_src_input_bpc can return 0 for platforms not
supporting DSC, which could theoretically cause issues in clamp()
due to a low limit being greater than the high limit.

Instead, return the minimum bpc supported by the source to prevent
such issues.

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/all/CA+G9fYtNfM399_=_ff81zeRJv=0+z7oFJfPGmJgTp6yrJmU+1w@mail.gmail.com/
Fixes: 160672b ("drm/i915/dp: Use clamp for pipe_bpp limits with DSC")
Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Tested-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250131041342.3086716-1-ankit.k.nautiyal@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit a67221b)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Author: aknautiyal

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

@@ -1791,7 +1791,7 @@ int intel_dp_dsc_max_src_input_bpc(struct intel_display *display)
 	if (DISPLAY_VER(display) == 11)
 		return 10;
 
-	return 0;
+	return intel_dp_dsc_min_src_input_bpc();
 }
 
 int intel_dp_dsc_compute_max_bpp(const struct intel_connector *connector,