drm/i915/dp: Use int for compressed BPP in dsc_compute_link_config()

Just use ints unless there are actual reasons to do otherwise. Here,
there are not.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b8f9aebc4e40afeed3d723f98cae96c9c927a480.1738327620.git.jani.nikula@intel.com