drm/radeon: enable bapm by default on desktop TN/RL boards

bapm enabled the GPU and CPU to share TDP headroom.  It was
disabled by default since some laptops hung when it was enabled
in conjunction with dpm.  It seems to be stable on desktop
boards and fixes hangs on boot with dpm enabled on certain
boards, so enable it by default on desktop boards.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=72921



Signed-off-by: Alex Deucher <alexander.deucher@amd.com>