drm/amd/display: update pipe topology log to support subvp

[why]
There is an ambiguity in subvp pipe topology log. The log doesn't show
subvp relation to main stream and it is not clear that certain stream
is an internal stream for subvp pipes.

[how]
Separate subvp pipe topology logging from main pipe topology. Log main
stream indices instead of the internal stream for subvp pipes.
The following is a sample log showing 2 streams with subvp enabled on
both:

   pipe topology update
 ________________________
| plane0  slice0  stream0|
|DPP1----OPP1----OTG1----|
| plane0  slice0  stream1|
|DPP0----OPP0----OTG0----|
|    (phantom pipes)     |
| plane0  slice0  stream0|
|DPP3----OPP3----OTG3----|
| plane0  slice0  stream1|
|DPP2----OPP2----OTG2----|
|________________________|

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Roman Li <roman.li@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>