drm/amd/display: Check for PSR in no memory request case

[Why]
When we have a PSR display, we will not be requesting data from memory anymore.
So we report back true for no memory request case.

[How]
Check for PSR by checking PSR version in link settings

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>