drm/radeon: fix 1 RB harvest config setup for TN/RL

commit dbfb00c3e7e18439f2ebf67fe99bf7a50b5bae1e upstream.

The logic was reversed from what the hw actually exposed.
Fixes graphics corruption in certain harvest configurations.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>