drm/i915/dp: Fix pipe BPP clamping due to HDR

drm/i915/dp: Fix pipe BPP clamping due to HDR

The pipe BPP value shouldn't be set outside of the source's / sink's
valid pipe BPP range, ensure this when increasing the minimum pipe BPP
value to 30 due to HDR.

While at it debug print if the HDR mode was requested for a connector by
setting the corresponding HDR connector property. This indicates
if the requested HDR mode could not be enabled, since the selected
pipe BPP is below 30, due to a sink capability or link BW limit.

v2:
- Also handle the case where the sink could support the target 30 BPP
  only in DSC mode due to a BW limit, but the sink doesn't support DSC
  or 30 BPP as a DSC input BPP. (Chaitanya)
- Debug print the connector's HDR mode in the link config dump, to
  indicate if a BPP >= 30 required by HDR couldn't be reached. (Ankit)
- Add Closes: trailer. (Ankit)
- Don't print the 30 BPP-outside of valid BPP range debug message if
  the min BPP is already > 30 (and so a target BPP >= 30 required
  for HDR is ensured).

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/7052
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15503
Fixes: ba49a4643cf53 ("drm/i915/dp: Set min_bpp limit to 30 in HDR mode")
Cc: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Cc: <stable@vger.kernel.org> # v6.18+
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com> # v1
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260209133817.395823-1-imre.deak@intel.com