On TGL the blending of all the streams have moved from DDI to
transcoder, so now every transcoder working over the same MST port must
send its stream to a master transcoder and master will send to DDI
respecting the time slots.

So here adding all the CRTCs that shares the same MST stream if
needed and computing their state again, it will pick the lowest
pipe/transcoder among the ones in the same stream to be master.

Most of the time skl_commit_modeset_enables() enables pipes in a
crescent order but due DDB overlapping it might not happen, this
scenarios will be handled in the next patch.

v2:
- Using recently added intel_crtc_state_reset() to set
mst_master_transcoder to invalid transcoder for all non gen12 & MST
code paths
- Setting lowest pipe/transcoder as master, previously it was the
first one but setting a predictable one will help in future MST e
port sync integration
- Moving to intel type as much as we can

v3:
- Now intel_dp_mst_master_trans_compute() returns the MST master transcoder
- Replaced stdbool.h by linux/types.h
- Skip the connector being checked in
intel_dp_mst_atomic_master_trans_check()
- Using pipe instead of transcoder to compute MST master

v4:
- renamed connector_state to conn_state

v5:
- Improved the parameters of intel_dp_mst_master_trans_compute() to
simply code
- Added call drm_atomic_add_affected_planes() in
intel_dp_mst_atomic_master_trans_check() as helper could not do it
for us
- Removed "if (ret)" left over from v3 changes

v6:
- handled ret == I915_MAX_PIPES case in compute

BSpec: 50493
BSpec: 49190
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191223010654.67037-2-jose.souza@intel.com