drm/dp_mst: Add kunit tests for drm_dp_get_vc_payload_bw()

Add kunit test cases for drm_dp_get_vc_payload_bw() with all the DP1.4
and UHBR link configurations.

v2:
- List test cases in decreasing rate,lane count order matching the
  corresponding DP Standard tables. (Ville)
- Add references to the DP Standard tables.
v3:
- Sort the testcases properly.
v4:
- Avoid 'stack frame size x exceeds limit y in
  drm_test_dp_mst_calc_pbn_div()' compiler warn. (LKP)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: kernel test robot <lkp@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v3)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231120125256.2433782-1-imre.deak@intel.com