BACKPORT: drm/i915/dp_mst: Handle error during DSC BW overhead/slice calculation

The MST branch device may not support the number of DSC slices a mode
requires, handle the error in this case.

Fixes: 4e0837a8 ("drm/i915/dp_mst: Account for FEC and DSC overhead during BW allocation")
Cc: stable@vger.kernel.org # v6.8+
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009110135.1216498-1-imre.deak@intel.com


(cherry picked from commit 802a69b6)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
(cherry picked from commit 69b3d872)

Conflicts:
   drivers/gpu/drm/i915/display/intel_dp_mst.c

BUG=b:325713868
TEST=CQ

Change-Id: Ie583e928685b58469beaa86624b41be4cc837cc2
Signed-off-by: Tim Van Patten <timvp@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/5948230


Reviewed-by: Drew Davenport <ddavenport@chromium.org>
Signed-off-by: Hubert Mazur <hmazur@google.com>