drm/i915/mst: remove unnecessary mst_stream_find_vcpi_slots_for_bpp()

mst_stream_find_vcpi_slots_for_bpp() has become a thin wrapper that
merely juggles parameters around. Remove it.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/abdd205087dc2ab0bdae09d7374d5f262f605aba.1738161945.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>