drm/i915/dp: Check min bpc DSC limits for dsc_force_bpc also

For DSC the min BPC is 8 for ICL+ and so the min pipe_bpp is 24.
Check this condition for cases where bpc is forced by debugfs flag
dsc_force_bpc. If the check fails, then WARN and ignore the debugfs
flag.

For MST case the pipe_bpp is already computed (hardcoded to be 24),
and this check is not required.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230817142459.89764-11-ankit.k.nautiyal@intel.com