drm/i915/dp: Limit the output link bpp in DSC mode

Limit the output link bpp in DSC mode to the link_config_limits
link.min_bpp_x16 .. max_bpp_x16 range the same way it's done in non-DSC
mode.  Atm this doesn't make a difference, the link bpp range being
0 .. max pipe bpp, but a follow-up patch will need a way to reduce max
link bpp below its current value.

v2:
- Add to_bpp_int_roundup() instead of open coding it. (Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230921195159.2646027-6-imre.deak@intel.com