drm/amd/display: Remove register from DCN35 DMCUB diagnostic collection

[Why]
These registers should not be read from driver and triggering the
security violation when DMCUB work times out and diagnostics are
collected blocks Z8 entry.

[How]
Remove the register read from DCN35.

Reviewed-by: Duncan Ma <duncan.ma@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>